Category: Mental Health Treatment

What is Perphenazine?

Published on by Andrew Marshall2 Comments

Introduction

Perphenazine is a typical antipsychotic drug. Chemically, it is classified as a piperazinyl phenothiazine. Originally marketed in the United States as Trilafon, it has been in clinical use for decades.

Perphenazine is roughly ten times as potent as chlorpromazine at the dopamine-2 (D2) receptor; thus perphenazine is considered a medium-potency antipsychotic.

Refer to Perphenazine Enanthate.

Medical Uses

In low doses it is used to treat agitated depression (together with an antidepressant). Fixed combinations of perphenazine and the tricyclic antidepressant amitriptyline in different proportions of weight exist (see Etrafon below). When treating depression, perphenazine is discontinued as fast as the clinical situation allows. Perphenazine has no intrinsic antidepressive activity. Several studies show that the use of perphenazine with fluoxetine (Prozac) in patients with psychotic depression is most promising, although fluoxetine interferes with the metabolism of perphenazine, causing higher plasma levels of perphenazine and a longer half-life. In this combination the strong antiemetic action of perphenazine attenuates fluoxetine-induced nausea and vomiting (emesis), as well as the initial agitation caused by fluoxetine. Both actions can be helpful for many patients.

Perphenazine has been used in low doses as a ‘normal’ or ‘minor’ tranquiliser in patients with a known history of addiction to drugs or alcohol, a practice which is now strongly discouraged.

Perphenazine has sedating and anxiolytic properties, making the drug useful for the treatment of agitated psychotic patients.

A valuable off-label indication is the short-time treatment of hyperemesis gravidarum, in which pregnant women experience violent nausea and vomiting. This problem can become severe enough to endanger the pregnancy. As perphenazine has not been shown to be teratogenic and works very well, it is sometimes given orally in the smallest possible dose.

Effectiveness

Perphenazine is used to treat psychosis (e.g. in people with schizophrenia and the manic phases of bipolar disorder). Perphenazine effectively treats the positive symptoms of schizophrenia, such as hallucinations and delusions, but its effectiveness in treating the negative symptoms of schizophrenia, such as flattened affect and poverty of speech, is unclear. Earlier studies found the typical antipsychotics to be ineffective or poorly effective in the treatment of negative symptoms, but two recent, large-scale studies found no difference between perphenazine and the atypical antipsychotics.

Side Effects

As a member of the phenothiazine type of antipsychotics, perphenazine shares in general all allergic and toxic side-effects of chlorpromazine. A 2015 systematic review of the data on perphenazine conducted by the Cochrane Collaboration concluded that “there were no convincing differences between perphenazine and other antipsychotics” in the incidence of adverse effects. Perphenazine causes early and late extrapyramidal side effects more often than placebo, and at a similar rate to other medium-potency antipsychotics and the atypical antipsychotic risperidone.

When used for its strong antiemetic or antivertignosic effects in cases with associated brain injuries, it may obscure the clinical course and interferes with the diagnosis. High doses of perphenazine can cause temporary dyskinesia. As with other typical antipsychotics, permanent or lasting tardive dyskinesia is a risk.

Discontinuation

The British National Formulary recommends a gradual withdrawal when discontinuing antipsychotics to avoid acute withdrawal syndrome or rapid relapse. Symptoms of withdrawal commonly include nausea, vomiting, and loss of appetite. Other symptoms may include restlessness, increased sweating, and trouble sleeping. Less commonly there may be a feeling of the world spinning, numbness, or muscle pains. Symptoms generally resolve after a short period of time.

There is tentative evidence that discontinuation of antipsychotics can result in psychosis. It may also result in reoccurrence of the condition that is being treated. Rarely tardive dyskinesia can occur when the medication is stopped.

Pharmacology

Pharmacokinetics

Perphenazine has an oral bioavailability of approximately 40% and a half-life of 8 to 12 hours (up to 20 hours), and is usually given in 2 or 3 divided doses each day. It is possible to give two-thirds of the daily dose at bedtime and one-third during breakfast to maximise hypnotic activity during the night and to minimise daytime sedation and hypotension without loss of therapeutic activity.

Formulations

It is sold under the brand names Trilafon (single drug) and Etrafon/Triavil/Triptafen (contains fixed dosages of amitriptyline). A brand name in Europe is Decentan pointing to the fact that perphenazine is approximately 10-times more potent than chlorpromazine. Usual oral forms are tablets (2, 4, 8, 16 mg) and liquid concentrate (4 mg/ml).

The ‘Perphenazine injectable USP’ solution is intended for deep intramuscular (IM) injection, for patients who are not willing to take oral medication or if the patient is unable to swallow. Due to a better bioavailability of the injection, two-thirds of the original oral dose is sufficient. The incidence of hypotension, sedation and extrapyramidal side-effects may be higher compared to oral treatment. IM-injections are appropriate for a few days, but oral treatment should start as soon as possible.

In many countries, depot forms of perphenazine exist (as perphenazine enanthate and perphenazine decanoate). One injection works for 1 to 4 weeks depending on the dose of the depot-injection. Depot-forms of perphenazine should not be used during the initial phase of treatment as the rare neuroleptic malignant syndrome may become more severe and uncontrollable with this form. Extrapyramidal side-effects may be somewhat reduced due to constant plasma-levels during depot-therapy. Also, patient compliance is sure, as many patients do not take their oral medication, particularly if feeling better once improvement in psychosis is achieved.

Interactions

Fluoxetine causes higher plasma levels and a longer elimination half-life of perphenazine, therefore a dose reduction of perphenazine might be necessary.

Perphenazine intensifies the central depressive action of drugs with such activity (tranquilizers, hypnotics, narcotics, antihistaminics, OTC-antiemetics etc.). A dose reduction of perphenazine or the other drug may be necessary.

In general, all neuroleptics may lead to seizures in combination with the opioid tramadol (Ultram).

Perphenazine may increase the insulin needs of diabetic patients. Monitor blood glucose levels of insulin-dependent patients regularly during long-term treatment.

What is Paroxetine?

Published on by Andrew Marshall19 Comments

Introduction

Paroxetine, sold under the brand names Paxil and Seroxat among others, is an antidepressant of the selective serotonin reuptake inhibitor (SSRI) class.

It is used to treat major depressive disorder, obsessive-compulsive disorder, panic disorder, social anxiety disorder, posttraumatic stress disorder (PTSD), generalised anxiety disorder (GAD) and premenstrual dysphoric disorder. It has also been used in the treatment of premature ejaculation and hot flashes due to menopause. It is taken by mouth.

Common side effects include drowsiness, dry mouth, loss of appetite, sweating, trouble sleeping, and sexual dysfunction. Serious side effects may include suicidal thoughts in those under the age of 25, serotonin syndrome, and mania. While the rate of side effects appears similar compared to other SSRIs and SNRIs, antidepressant discontinuation syndromes may occur more often. Use in pregnancy is not recommended, while use during breastfeeding is relatively safe. It is believed to work by blocking the re-uptake of the chemical serotonin by neurons in the brain.

Paroxetine was approved for medical use in the United States in 1992 and initially sold by GlaxoSmithKline. It is on the World Health Organisation’s List of Essential Medicines. It is available as a generic medication. In 2019, it was the 78th most commonly prescribed medication in the United States, with more than 9 million prescriptions. In 2018, it was in the top 10 of most prescribed antidepressants in the United States. In 2012, the United States Department of Justice fined GlaxoSmithKline $3 billion for withholding data, unlawfully promoting use in those under 18, and preparing an article that misleadingly reported the effects of paroxetine in adolescents with depression following its clinical trial study 329.

Medical Uses

Paroxetine is primarily used to treat major depressive disorder (MDD), obsessive-compulsive disorder (OCD), PTSD, social anxiety disorder, and panic disorder. It is also occasionally used for agoraphobia, GAD, premenstrual dysphoric disorder and menopausal hot flashes.

Depression

A variety of meta analyses have been conducted to evaluate the efficacy of paroxetine in depression. They have variously concluded that paroxetine is superior or equivalent to placebo and that it is equivalent or inferior to other antidepressants. Despite this, there was no clear evidence that paroxetine was better or worse compared with other antidepressants at increasing response to treatment at any point in time.

Anxiety Disorders

Paroxetine was the first antidepressant approved in the United States for the treatment of panic disorder. Several studies have concluded that paroxetine is superior to placebo in the treatment of panic disorder.

Paroxetine has demonstrated efficacy for the treatment of social anxiety disorder in adults and children. It is also beneficial for people with co-occurring social anxiety disorder and alcohol use disorder. It appears to be similar to a number of other SSRIs.

Paroxetine is used in the treatment of OCD. Comparative efficacy of paroxetine is equivalent to that of clomipramine and venlafaxine. Paroxetine is also effective for children with OCD.

Paroxetine is approved for treatment of PTSD in the United States, Japan and Europe. In the United States it is approved for short-term use.

Paroxetine is also Food and Drug Administration (FDA)-approved for GAD.

Menopausal Hot Flashes

In 2013, low-dose paroxetine was approved in the US for the treatment of moderate-to-severe vasomotor symptoms such as hot flashes and night sweats associated with menopause. At the low dose used for menopausal hot flashes, side effects are similar to placebo and dose tapering is not required for discontinuation.

Fibromyalgia

Studies have also shown paroxetine “appears to be well-tolerated and improve the overall symptomatology in patients with fibromyalgia” but is less robust in helping with the pain involved.

Adverse Effects

Common side effects include drowsiness, dry mouth, loss of appetite, sweating, trouble sleeping, and sexual dysfunction. Serious side effects may include suicide in those under the age of 25, serotonin syndrome, and mania. While the rate of side effects appears similar compared to other SSRIs and SNRIs, antidepressant discontinuation syndromes may occur more often. Use in pregnancy is not recommended while use during breastfeeding is relatively safe.

Paroxetine shares many of the common adverse effects of SSRIs, including (with the corresponding rates seen in people treated with placebo in parentheses):

  • Nausea 26% (9%).
  • Diarrhoea 12% (8%).
  • Constipation 14% (9%).
  • Dry mouth 18% (12%).
  • Somnolence 23% (9%).
  • Insomnia 13% (6%).
  • Headache 18% (17%).
  • Hypomania 1% (0.3%).
  • Blurred vision 4% (1%).
  • Loss of appetite 6% (2%).
  • Nervousness 5% (3%).
  • Paraesthesia 4% (2%).
  • Dizziness 13% (6%).
  • Asthenia (weakness; 15% (6%)).
  • Tremor 8% (2%).
  • Sweating 11% (2%).
  • Sexual dysfunction (≥10% incidence).

Most of these adverse effects are transient and go away with continued treatment. Central and peripheral 5-HT3 receptor stimulation is believed to result in the gastrointestinal effects observed with SSRI treatment. Compared to other SSRIs, it has a lower incidence of diarrhoea, but a higher incidence of anticholinergic effects (e.g. dry mouth, constipation, blurred vision, etc.), sedation/somnolence/drowsiness, sexual side effects, and weight gain.

Due to reports of adverse withdrawal reactions upon terminating treatment, the Committee for Medicinal Products for Human Use (CHMP) at the European Medicines Agency recommends gradually reducing over several weeks or months if the decision to withdraw is made (Refer to discontinuation syndrome below).

Mania or hypomania may occur in 1% of patients with depression and up to 12% of patients with bipolar disorder. This side effect can occur in individuals with no history of mania but it may be more likely to occur in those with bipolar or with a family history of mania.

Suicide

Like other antidepressants, paroxetine may increase the risk of suicidal thinking and behaviour in people under the age of 25. The FDA conducted a statistical analysis of paroxetine clinical trials in children and adolescents in 2004 and found an increase in suicidality and ideation as compared to placebo, which was observed in trials for both depression and anxiety disorders. In 2015 a paper published in The BMJ that reanalysed the original case notes argued that in Study 329, assessing paroxetine and imipramine against placebo in adolescents with depression, the incidence of suicidal behaviour had been under-reported and the efficacy exaggerated for paroxetine.

Sexual Dysfunction

Sexual dysfunction, including loss of libido, anorgasmia, lack of vaginal lubrication, and erectile dysfunction, is one of the most commonly encountered adverse effects of treatment with paroxetine and other SSRIs. While early clinical trials suggested a relatively low rate of sexual dysfunction, more recent studies in which the investigator actively inquires about sexual problems suggest that the incidence is higher than 70%. Symptoms of sexual dysfunction have been reported to persist after discontinuing SSRIs, although this is thought to be occasional.

Pregnancy

Antidepressant exposure (including paroxetine) is associated with shorter duration of pregnancy (by three days), increased risk of preterm delivery (by 55%), lower birth weight (by 75 g or 2.6 oz), and lower Apgar scores (by <0.4 points). The American College of Obstetricians and Gynaecologists recommends that for pregnant women and women planning to become pregnant, paroxetine “be avoided, if possible”, as it may be associated with increased risk of birth defects.

Babies born to women who used paroxetine during the first trimester have an increased risk of cardiovascular malformations, primarily ventricular and atrial septal defects (VSDs and ASDs). Unless the benefits of paroxetine justify continuing treatment, consideration should be given to stopping or switching to another antidepressant. Paroxetine use during pregnancy is associated with about 1.5-1.7-fold increase in congenital birth defects, in particular, heart defects, cleft lip and palate, clubbed feet or any birth defects.

Antidepressant Discontinuation Syndrome

Refer to Antidepressant Discontinuation Syndrome.

Many psychoactive medications can cause withdrawal symptoms upon discontinuation from administration. Evidence has shown that paroxetine has among the highest incidence rates and severity of withdrawal syndrome of any medication of its class. Common withdrawal symptoms for paroxetine include nausea, dizziness, lightheadedness and vertigo; insomnia, nightmares and vivid dreams; feelings of electricity in the body, as well as rebound depression and anxiety. Liquid formulation of paroxetine is available and allows a very gradual decrease of the dose, which may prevent discontinuation syndrome. Another recommendation is to temporarily switch to fluoxetine, which has a longer half-life and thus decreases the severity of discontinuation syndrome.

In 2002, the FDA published a warning regarding “severe” discontinuation symptoms among those terminating paroxetine treatment, including paraesthesia, nightmares, and dizziness. The FDA also warned of case reports describing agitation, sweating, and nausea. In connection with a Glaxo spokesperson’s statement that withdrawal reactions occur only in 0.2% of patients and are “mild and short-lived”, the International Federation of Pharmaceutical Manufacturers Associations said GSK had breached two of the Federation’s codes of practice.

Paroxetine prescribing information posted at GlaxoSmithKline has been updated related to the occurrence of a discontinuation syndrome, including serious discontinuation symptoms.

Overdose

Acute overdosage is often manifested by emesis, lethargy, ataxia, tachycardia, and seizures. Plasma, serum, or blood concentrations of paroxetine may be measured to monitor therapeutic administration, confirm a diagnosis of poisoning in hospitalized patients or to aid in the medicolegal investigation of fatalities. Plasma paroxetine concentrations are generally in a range of 40-400 μg/L in persons receiving daily therapeutic doses and 200-2,000 μg/L in poisoned patients. Postmortem blood levels have ranged from 1-4 mg/L in acute lethal overdose situations. Along with the other SSRIs, sertraline and fluoxetine, paroxetine is considered a low-risk drug in cases of overdose.

Interactions

Interactions with other drugs acting on the serotonin system or impairing the metabolism of serotonin may increase the risk of serotonin syndrome or neuroleptic malignant syndrome (NMS)-like reaction. Such reactions have been observed with SNRIs and SSRIs alone, but particularly with concurrent use of triptans, MAO inhibitors, antipsychotics, or other dopamine antagonists.

The prescribing information states that paroxetine should “not be used in combination with an MAOI (including linezolid, an antibiotic which is a reversible non-selective MAOI), or within 14 days of discontinuing treatment with an MAOI”, and should not be used in combination with pimozide, thioridazine, tryptophan, or warfarin.

Paroxetine interacts with the following cytochrome P450 enzymes:

  • CYP2D6 for which it is both a substrate and a potent inhibitor.
  • CYP2B6 (strong) inhibitor.
  • CYP3A4 (weak) inhibitor.
  • CYP1A2 (weak) inhibitor.
  • CYP2C9 (weak) inhibitor.
  • CYP2C19 (weak) inhibitor.

Paroxetine has been shown to be an inhibitor of G protein-coupled receptor kinase 2 (GRK2).

Pharmacology

Pharmacodynamics

Paroxetine is the most potent and one of the most specific selective serotonin (5-hydroxytryptamine, 5-HT) reuptake inhibitors (SSRIs). It also binds to the allosteric site of the serotonin transporter, similarly, but less potently, than escitalopram. Paroxetine also inhibits the reuptake of norepinephrine to a lesser extent (<50 nmol/L). Based on evidence from four weeks of administration in rats, the equivalent of 20 mg paroxetine taken once daily occupies approximately 88% of serotonin transporters in the prefrontal cortex.

Pharmacokinetics

Paroxetine is well-absorbed following oral administration. It has an absolute bioavailability of about 50%, with evidence of a saturable first pass effect. When taken orally, it achieves maximum concentration in about 6-10 hours and reaches steady-state in 7-14 days. Paroxetine exhibits significant interindividual variations in volume of distribution and clearance. Less than 2% of an oral dose is excreted in urine unchanged.

Paroxetine is a mechanism-based inhibitor of CYP2D6.

Society and Culture

GlaxoSmithKline has paid substantial fines, paid settlements in class-action lawsuits, and become the subject of several highly critical books about its marketing of paroxetine, in particular the off-label marketing of paroxetine for children, the suppression of negative research results relating to its use in children, and allegations that it failed to warn consumers of substantial withdrawal effects associated with use of the drug. Paroxetine was approved for medical use in the United States in 1992 and initially sold by GlaxoSmithKline. It is currently available as a generic medication. In 2017, it was the 68th most commonly prescribed medication in the United States, with more than eleven million prescriptions. The United States Department of Justice fined GlaxoSmithKline $3 billion in 2012, for withholding data, unlawfully promoting use in those under 18, and preparing an article that misleadingly reported the effects of paroxetine in adolescents with depression following its clinical trial study 329.

Marketing

In early 2004, GSK agreed to settle charges of consumer fraud for $2.5 million. The legal discovery process also uncovered evidence of deliberate, systematic suppression of unfavourable Paxil research results. One of GSK’s internal documents read, “It would be commercially unacceptable to include a statement that efficacy [in children] had not been demonstrated, as this would undermine the profile of paroxetine”.

In 2012 the US Justice Department announced that GSK agreed to plead guilty and pay a $3 billion fine, in part for promoting the use of Paxil for children.

On 12 February 2016, the UK Competition and Markets Authority imposed record fines of £45 million on companies which were found to have infringed European Union and UK Competition law by entering into agreements to delay the market entry of generic versions of the drug in the UK. GlaxoSmithKline received the bulk of the fines, being fined £37,600,757. Other companies, which produce generics, were issued fines which collectively total £7,384,146. UK public health services are likely to claim damages for being overcharged in the period where the generic versions of the drug were illegally blocked from the market, as the generics are over 70% less expensive. GlaxoSmithKline may also face actions from other generics manufacturers who incurred loss as a result of the anticompetitive conduct. On 18 April 2016, appeals were lodged with the Competition Appeal Tribunal by the companies which were fined.

GSK marketed paroxetine through television advertisements throughout the late 1990s and early 2000s. Commercials also aired for the CR version of the drug beginning in 2003.

Sales

In 2007, paroxetine was ranked 94th on the list of bestselling drugs, with over $1 billion in sales. In 2006, paroxetine was the fifth-most prescribed antidepressant in the US retail market, with more than 19.7 million prescriptions. In 2007, sales had dropped slightly to 18.1 million but paroxetine remained the fifth-most prescribed antidepressant in the US.

Trade Names

Trade names include Aropax, Brisdelle, Deroxat, Paxil, Pexeva, Paxtine, Paxetin, Paroxat, Paraxyl, Sereupin, Daparox and Seroxat.

Research

Several studies have suggested that paroxetine can be used in the treatment of premature ejaculation. In particular, intravaginal ejaculation latency time (IELT) was found to increase with 6- to 13-fold, which was somewhat longer than the delay achieved by the treatment with other SSRIs (fluvoxamine, fluoxetine, sertraline, and citalopram). However, paroxetine taken acutely (“on demand”) 3-10 hours before coitus resulted only in a “clinically irrelevant and sexually unsatisfactory” 1.5-fold delay of ejaculation and was inferior to clomipramine, which induced a fourfold delay.

There is also evidence that paroxetine may be effective in the treatment of compulsive gambling and hot flashes.

Benefits of paroxetine prescription for diabetic neuropathy or chronic tension headache are uncertain.

Although the evidence is conflicting, paroxetine may be effective for the treatment of dysthymia, a chronic disorder involving depressive symptoms for most days of the year.

There is evidence to support that paroxetine selectively binds to and inhibits G protein-coupled receptor kinase 2 (GRK2). Since GRK2 regulates the activity of the beta adrenergic receptor, which becomes desensitised in cases of heart failure, paroxetine (or a paroxetine derivative) could be used as a heart failure treatment in the future.

Paroxetine has been deemed to have dmoad activity.

What is Metacognitive Training?

Published on by Andrew Marshall1 Comment

Introduction

Metacognitive training, (MCT), is an approach for treating the symptoms of psychosis in schizophrenia, especially delusions, which has been adapted for other disorders such as depression, obsessive-compulsive disorder and borderline personality disorder over the years (see below and external links for free download).

It was developed by Steffen Moritz and Todd Woodward. The intervention is based on the theoretical principles of cognitive behavioural therapy (CBT), but focuses in particular on problematic thinking styles (cognitive biases) that are associated with the development and maintenance of positive symptoms, e.g. overconfidence in errors and jumping to conclusions. Metacognitive training exists as a group training (MCT) and as an individualized intervention (MCT+).

Refer to Metacognitive Therapy.

Background

Metacognition can be defined as “thinking about thinking”. Over the course of the training, cognitive biases subserving positive symptoms are identified and corrected. The current empirical evidence assumes a connection between certain cognitive biases, such as jumping to conclusions, and the development and maintenance of psychosis. Accordingly, correcting these problematic/unhelpful thinking styles should lead to a reduction of symptoms.

Intervention

In eight training units (modules) and two additional modules, examples of “cognitive traps”, which can promote the development and maintenance of the positive symptoms of schizophrenia, are presented to patients in a playful way. Patients are instructed to critically reflect on their thought patterns, which may contribute to problematic behaviours, and to implement the contents of the training in everyday life. MCT deals with the following problematic styles of thinking: monocausal attributions, jumping to conclusions, inflexibility, problems in social cognition, overconfidence for memory errors and depressive thought patterns. The additional modules deal with stigma and low self-esteem. Individualised metacognitive training (MCT+) targets the same symptoms and cognitive biases as the group training, but is more flexible in that it allows discussion of individualised topics. The treatment materials for the group training can be obtained free of charge in over 30 languages from the website.

Efficacy

A recent meta-analysis found significant improvements for positive symptoms and delusions, as well as the acceptance of the training. These findings have been replicated in 2018 and 2019. An older meta-analysis based on a smaller number of studies found a small effect, which reached significance when newer studies were considered. Individual studies provide evidence for the long-term effectiveness of the approach beyond the immediate treatment period. MCT is recommended as an evidence-based treatment by the Royal Australian and New Zealand College of Psychiatrists as well as the German Association for Psychiatry, Psychotherapy and Psychosomatics.

Adaptations to other Disorders

Since its introduction, MCT has been adapted to other mental disorders. Empirical studies have been carried out for borderline personality disorder, obsessive-compulsive disorder (self-help approach), depression, bipolar disorders, and problem gambling.

Links (External)

What is Metacognitive Therapy?

Published on by Andrew Marshall1 Comment

Introduction

Metacognitive therapy (MCT) is a psychotherapy focused on modifying metacognitive beliefs that perpetuate states of worry, rumination and attention fixation.

It was created by Adrian Wells based on an information processing model by Wells and Gerald Matthews. It is supported by scientific evidence from a large number of studies.

The goals of MCT are first to discover what patients believe about their own thoughts and about how their mind works (called metacognitive beliefs), then to show the patient how these beliefs lead to unhelpful responses to thoughts that serve to unintentionally prolong or worsen symptoms, and finally to provide alternative ways of responding to thoughts in order to allow a reduction of symptoms. In clinical practice, MCT is most commonly used for treating anxiety disorders such as social anxiety disorder, generalised anxiety disorder (GAD), health anxiety, obsessive compulsive disorder (OCD) and post-traumatic stress disorder (PTSD) as well as depression – though the model was designed to be transdiagnostic (meaning it focuses on common psychological factors thought to maintain all psychological disorders).

Refer to Metacognitive Training.

Brief History

Metacognition, Greek for “after” (meta) “thought” (cognition), refers to the human capacity to be aware of and control one’s own thoughts and internal mental processes. Metacognition has been studied for several decades by researchers, originally as part of developmental psychology and neuropsychology. Examples of metacognition include a person knowing what thoughts are currently in their mind and knowing where the focus of their attention is, and a person’s beliefs about their own thoughts (which may or may not be accurate). The first metacognitive interventions were devised for children with attentional disorders in the 1980s.

Model of Mental Disorders

Self-Regulatory Executive Function Model

In the metacognitive model, symptoms are caused by a set of psychological processes called the cognitive attentional syndrome (CAS). The CAS includes three main processes, each of which constitutes extended thinking in response to negative thoughts. These three processes are:

  • Worry/rumination.
  • Threat monitoring.
  • Coping behaviours that backfire.

All three are driven by patients’ metacognitive beliefs, such as the belief that these processes will help to solve problems, although the processes all ultimately have the unintentional consequence of prolonging distress. Of particular importance in the model are negative metacognitive beliefs, especially those concerning the uncontrollability and dangerousness of some thoughts. Executive functions are also believed to play a part in how the person can focus and refocus on certain thoughts and mental modes. These mental modes can be categorised as object mode and metacognitive mode, which refers to the different types of relationships people can have towards thoughts. All of the CAS, the metacognitive beliefs, the mental modes and the executive function together constitute the self-regulatory executive function model (S-REF). This is also known as the metacognitive model. In more recent work, Wells has described in greater detail a metacognitive control system of the S-REF aimed at advancing research and treatment using metacognitive therapy.

Therapeutic Intervention

MCT is a time-limited therapy which usually takes place between 8-12 sessions. The therapist uses discussions with the patient to discover their metacognitive beliefs, experiences and strategies. The therapist then shares the model with the patient, pointing out how their particular symptoms are caused and maintained.

Therapy then proceeds with the introduction of techniques tailored to the patient’s difficulties aimed at changing how the patient relates to thoughts and that bring extended thinking under control. Experiments are used to challenge metacognitive beliefs (e.g. “You believe that if you worry too much you will go ‘mad’ – let’s try worrying as much as possible for the next five minutes and see if there is any effect”) and strategies such as attentional training technique and detached mindfulness (this is a distinct strategy from various other mindfulness techniques).

Research

Clinical trials (including randomised controlled trials) have found MCT to produce large clinically significant improvements across a range of mental health disorders, although as of 2014 the total number of subjects studied is small and a meta-analysis concluded that further study is needed before strong conclusions can be drawn regarding effectiveness. A 2015 special issue of the journal Cognitive Therapy and Research was devoted to MCT research findings.

A 2018 meta-analysis confirmed the effectiveness of MCT in the treatment of a variety of psychological complaints with depression and anxiety showing high effect sizes. It concluded (Morina & Normann, 2018):

“Our findings indicate that MCT is an effective treatment for a range of psychological complaints. To date, strongest evidence exists for anxiety and depression. Current results suggest that MCT may be superior to other psychotherapies, including cognitive behavioral interventions. However, more trials with larger number of participants are needed in order to draw firm conclusions.”

In 2020, a study showed superior effectiveness in MCT over CBT in the treatment of depression. It summarised (Callesen et al., 2020):

“MCT appears promising and might offer a necessary advance in depression treatment, but there is insufficient evidence at present from adequately powered trials to assess the relative efficacy of MCT compared with CBT in depression.”

In 2018-2020, a research topic in the journal Frontiers in Psychology highlighted the growing experimental, clinical, and neuropsychological evidence base for MCT.

References

Morina, N. & Normann, N. (2018) The Efficacy of Metacognitive Therapy: A Systematic Review and Meta-Analysis. Frontiers in Psychology. 9:2211. doi:10.3389/fpsyg.2018.02211.

Callesen, P., Reeves, D., Heal, C. & Wells, A. (2020) Metacognitive Therapy versus Cognitive Behaviour Therapy in Adults with Major Depression: A Parallel Single-Blind Randomised Trial. Scientific Reports. 10(1):7878.

What is Mazindol?

Published on by Andrew Marshall2 Comments

Introduction

Mazindol (brand names Mazanor, Sanorex) is a stimulant drug which is used as an appetite suppressant.

It was developed by Sandoz-Wander in the 1960s.

Medical Uses

Mazindol is used in short-term (i.e. a few weeks) treatment of obesity, in combination with a regimen of weight reduction based on caloric restriction, exercise, and behaviour modification in people with a body mass index greater than 30, or in those with a body mass index greater than 27 in the presence of risk factors such as hypertension, diabetes, or hyperlipidaemia. Mazindol is not currently available as a commercially marketed and US Food and Drug Administration (FDA)-regulated prescription agent for the treatment of obesity.

There is a Swiss study investigating its efficacy in treating ADHD.

Pharmacology

Mazindol is a sympathomimetic amine, which is similar to amphetamine. It stimulates the central nervous system, which increases heart rate and blood pressure, and decreases appetite. Sympathomimetic anorectics (appetite suppressants) are used in the short-term treatment of obesity. Their appetite-reducing effect tends to decrease after a few weeks of treatment. Because of this, these medicines are useful only during the first few weeks of a weight-loss program.

Although the mechanism of action of the sympathomimetics in the treatment of obesity is not fully known, these medications have pharmacological effects similar to those of amphetamines. Like other sympathomimetic appetite suppressants, mazindol is thought to act as a reuptake inhibitor of norepinephrine. In addition, it inhibits dopamine and serotonin reuptake. The recommended dosage is 2 mg per day for 90 days in patients 40 kg overweight and under; 4 mg a day in patients more than 50 kg overweight; divided into two doses separated by a 12-hour window between each dose.

Overdose

Symptoms of a mazindol overdose include: restlessness, tremor, rapid breathing, confusion, hallucinations, panic, aggressiveness, nausea, vomiting, diarrhoea, an irregular heartbeat, and seizures.

Analogues

From available QSAR data, the following trends are apparent:

  • Desoxylation of the tertiary alcohol in mazindol improves DAT and SERT binding without substantially reducing NET affinity.
  • Removal of the p-chlorine atom from the phenyl ring of mazindol increases NET affinity and substantially reduces DAT and SERT affinity.
  • Expansion of the imidazoline ring system in mazindol to the corresponding six-membered homolog increases DAT affinity by ~10 fold.
  • Replacement of the phenyl moiety with a naphthyl ring system results in a ~50 fold increase in SERT affinity without significant decreases in NET or DAT affinities.
  • Halogenation of 3′ and/or 4′ position of the phenyl ring of mazindol results in increased potency at NET, DAT, and SERT.
  • Fluorination of the 7′ position of the tricyclic phenyl ring results in a ~2 fold increase in binding affinity to the DAT.

Research

As of 2016 mazindol was being studied in clinical trials for attention-deficit hyperactivity disorder.

What is Lamotrigine?

Published on by Andrew Marshall8 Comments

Introduction

Lamotrigine, sold as the brand name Lamictal among others, is an anticonvulsant medication used to treat epilepsy and to delay or prevent the recurrence of depressive episodes in bipolar disorder. For epilepsy, this includes focal seizures, tonic-clonic seizures, and seizures in Lennox-Gastaut syndrome. In bipolar disorder, lamotrigine has not been shown to reliably treat acute depression; but for patients with bipolar disorder who are not currently symptomatic, it appears to be effective in reducing the risk of future episodes of depression.

Common side effects include nausea, sleepiness, headache, vomiting, trouble with coordination, and rash. Serious side effects include lack of red blood cells, increased risk of suicide, Stevens-Johnson syndrome, and allergic reactions. Concerns exist that use during pregnancy or breastfeeding may result in harm. Lamotrigine is a phenyltriazine, making it chemically different from other anticonvulsants. Its mechanism of action is not clear, but it appears to inhibit release of excitatory neurotransmitters via voltage-sensitive sodium channels in neurons.

Lamotrigine was first marketed in the United Kingdom in 1991, and approved for use in the United States in 1994. It is on the World Health Organization’s List of Essential Medicines. In 2019, it was the 71st most commonly prescribed medication in the United States, with more than 10 million prescriptions.

Brief History

  • 1991 – Lamotrigine is first used in the United Kingdom as an anticonvulsant medication.
  • December 1994 – Lamotrigine was first approved for use in the United States and, that for the treatment of partial seizures.
  • August 1998 – For use as adjunctive treatment of Lennox-Gastaut syndrome in paediatric and adult patients, new dosage form: chewable dispersible tablets.
  • December 1998 – For use as monotherapy for treatment of partial seizures in adult patients when converting from a single enzyme-inducing anticonvulsant drug.
  • January 2003 – For use as adjunctive therapy for partial seizures in paediatric patients as young as two years of age.
  • June 2003 – Approved for maintenance treatment of Bipolar II disorder; the first such medication since lithium.
  • January 2004 – For use as monotherapy for treatment of partial seizures in adult patients when converting from the anti-epileptic drug valproate (including valproic acid).

Medical Uses

Epilepsy

Lamotrigine is considered a first-line drug for primary generalized tonic-clonic seizures (includes simple partial, complex partial, and secondarily generalized seizures such as focal-onset tonic-clonic seizures). It is also used as an alternative or adjuvant medication for partial seizures, such as absence seizure, myoclonic seizure, and atonic seizures. A 2020 review on the use of Lamotrigine as an add-on therapy for drug resistant generalized tonic-clonic seizures was unable to come to conclusions to inform clinical practice. Although low-certainty evidence suggest that it reduces generalised tonic-clonic seizures by 50% the level of uncertainty indicates that the actual findings could be significantly different. Another 2020 Cochrane review examining the use of lamotrigine as an add-on therapy for drug-resistant focal epilepsy found it to be effective for reducing seizure frequency and was well tolerated.

Lennox-Gastaut Syndrome

Lamotrigine is one of a small number of FDA-approved therapies for the form of epilepsy known as Lennox-Gastaut syndrome. It reduces the frequency of LGS seizures, and is one of two medications known to decrease the severity of drop attacks. Combination with valproate is common, but this increases the risk of lamotrigine-induced rash, and necessitates reduced dosing due to the interaction of these drugs.

Bipolar Disorder

Lamotrigine is approved in the US for maintenance treatment of bipolar I disorder and bipolar II disorder. While the anticonvulsants carbamazepine and valproate are predominantly antimanics, lamotrigine has demonstrated efficacy only in preventing or reducing the risk of recurrent depressive episodes of bipolar disorder. The drug seems ineffective in the treatment of current rapid-cycling, acute mania, or acute depression in bipolar disorder.

Lamotrigine has not demonstrated clear efficacy in treating acute mood episodes, either mania or depression. It has not demonstrated effectiveness in treating acute mania, and there is controversy regarding the drug’s effectiveness in treating acute bipolar depression. A paper written in 2008 by Nassir et al. reviewed evidence from trials that were unpublished and not referenced in the 2002 APA guidelines, and it concludes that lamotrigine has “very limited, if any, efficacy in the treatment of acute bipolar depression”. A 2008 paper by Calabrese et al. examined much of the same data, and found that in five placebo-controlled studies, lamotrigine did not significantly differ from placebo in the treatment of bipolar depression. However, in a meta-analysis of these studies conducted in 2008, Geddes, Calabrese and Goodwin found that lamotrigine was effective in individuals with bipolar depression, with a number needed to treat (NNT) of 11, or 7 in severe depression.

A 2013 review about lamotrigine concluded that it is recommended in bipolar maintenance when depression is prominent and that more research is needed in regard to its role in the treatment of acute bipolar depression and unipolar depression. No information to recommend its use in other psychiatric disorders was found.

Schizophrenia

Lamotrigine, as a monotherapy, is not substantially effective against schizophrenia. However; various publications and textbooks have expressed that lamotrigine could be added to clozapine as augmentation therapy against partial or non-responding schizophrenic patients. Patients had statistically significant improvements in positive, negative and affective symptoms. Lamotrigine does not have a statistically significant effect with antipsychotics other than clozapine, such as: olanzapine, risperidone, haloperidol, zuclopenthixol, etc.

Other Uses

Off-label uses include the treatment of peripheral neuropathy, trigeminal neuralgia, cluster headaches, migraines, visual snow, and reducing neuropathic pain, although a systematic review conducted in 2013 concluded that well-designed clinical trials have shown no benefit for lamotrigine in neuropathic pain. Off-label psychiatric usage includes the treatment of treatment-resistant obsessive-compulsive disorder, depersonalisation disorder, hallucinogen persisting perception disorder, schizoaffective disorder, and borderline personality disorder.

It has not been shown to be useful in post-traumatic stress disorder.

Side Effects

Lamotrigine prescribing information has a black box warning about life-threatening skin reactions, including Stevens-Johnson syndrome (SJS), DRESS syndrome, and toxic epidermal necrolysis (TEN). The manufacturer states that nearly all cases appear in the first two to eight weeks of therapy. Patients should seek medical attention for any unexpected skin rash, as its presence is an indication of a possible serious or even deadly side effect of the drug. Not all rashes that occur while taking lamotrigine progress to SJS or TEN. Between 5 and 10% of patients will develop a rash, but only one in a thousand patients will develop a serious rash. Rash and other skin reactions are more common in children, so this medication is often reserved for adults. For patients whose lamotrigine has been stopped after development of a rash, rechallenge with lamotrigine is also a viable option. However, it is not applicable for very serious cases. The incidence of these eruptions increases in patients who are currently on, or recently discontinued a valproate-type anticonvulsant drug, as these medications interact in such a way that the clearance of both is decreased and the effective dose of lamotrigine is increased.

Side effects such as rash, fever, and fatigue are very serious, as they may indicate incipient SJS, TEN, DRESS syndrome, or aseptic meningitis. Other side effects include loss of balance or coordination, double vision, crossed eyes, pupil constriction, blurred vision, dizziness and lack of coordination, drowsiness, insomnia, anxiety, vivid dreams or nightmares, dry mouth, mouth ulcers, memory problems, mood changes, itchiness, runny nose, cough, nausea, indigestion, abdominal pain, weight loss, missed or painful menstrual periods, and vaginitis. The side-effects profile varies for different patient populations. Overall adverse effects in treatment are similar between men, women, geriatric, paediatric and racial groups.

Lamotrigine has been associated with a decrease in white blood cell count (leukopenia). Lamotrigine does not prolong QT/QTc in TQT studies in healthy subjects.

In people taking antipsychotics, cases of lamotrigine-precipitated neuroleptic malignant syndrome have been reported.

In 2018, the FDA required a new warning for the risk of hemophagocytic lymphohistiocytosis. This reaction can occur between days to weeks after starting the treatment.

Women

Women are more likely than men to have side effects. This is the opposite of most other anticonvulsants.

Some evidence shows interactions between lamotrigine and female hormones, which can be of particular concern for women on oestrogen-containing hormonal contraceptives. Ethinylestradiol, an ingredient of such contraceptives, has been shown to decrease serum levels of lamotrigine. Women starting an oestrogen-containing oral contraceptive may need to increase the dosage of lamotrigine to maintain its level of efficacy. Likewise, women may experience an increase in lamotrigine side effects upon discontinuation of birth control pills. This may include the “pill-free” week where lamotrigine serum levels have been shown to increase twofold.

Pregnancy and Breastfeeding

Many studies have found no association between lamotrigine exposure in utero and birth defects, while those that have found an association have found only slight associations with minor malformations such as cleft palates. Review studies have found that overall rates of congenital malformations in infants exposed to lamotrigine in utero are relatively low (1-4%), which is similar to the rate of malformations in the general population. It is known that lamotrigine is a weak inhibitor of human dihydrofolate reductase (DHFR) and other, more powerful, human DHFR inhibitors such as methotrexate are known to be teratogenic.

Lamotrigine is expressed in breast milk; the manufacturer does not recommend breastfeeding during treatment. However, recent studies suggest that lamotrigine is safe to use while breastfeeding. A frequently updated review of scientific literature rates lamotrigine as L3: moderately safe.

Other Types of Effects

Lamotrigine binds to melanin-containing tissues such as the iris of the eye or melanin-rich skin. The long-term consequences of this are unknown.

GlaxoSmithKline investigated lamotrigine for the treatment of ADHD with inconclusive results. No detrimental effects on cognitive function were observed; however, the only statistical improvement in core ADHD symptoms was an improvement on a Paced Auditory Serial Addition Test (PASAT) that measures auditory processing speed and calculation ability. Another study reported that lamotrigine might be a safe and effective treatment option for adult ADHD comorbid with bipolar and recurrent depression.

Lamotrigine is known to affect sleep. Studies with small numbers of patients (10-15) reported that lamotrigine increases the duration of REM sleep, decreases the number of phase shifts, and decreases the duration of slow-wave sleep, and that there was no effect on vigilance, daytime somnolence and cognitive function. However, a retrospective study of 109 patients’ medical records found that 6.7% of patients experienced an “alerting effect” resulting in intolerable insomnia, for which the treatment had to be discontinued.

Lamotrigine can induce a type of seizure known as a myoclonic jerk, which tends to happen soon after the use of the medication. When used in the treatment of myoclonic epilepsies such as juvenile myoclonic epilepsy, lower doses (and lower plasma levels) are usually needed, as even moderate doses of this drug can induce seizures, including tonic-clonic seizures, which can develop into status epilepticus, which is a medical emergency. It can also cause myoclonic status epilepticus.

In overdose, lamotrigine can cause uncontrolled seizures in most people. Reported results in overdoses involving up to 15 g include increased seizures, coma, and death.

Pharmacology

Mechanism of Action

Lamotrigine is a member of the sodium channel blocking class of antiepileptic drugs. This may suppress the release of glutamate and aspartate, two dominant excitatory neurotransmitters in the central nervous system. It is generally accepted to be a member of the sodium channel blocking class of antiepileptic drugs, but it could have additional actions, since it has a broader spectrum of action than other sodium channel antiepileptic drugs such as phenytoin and is effective in the treatment of the depressed phase of bipolar disorder, whereas other sodium channel-blocking antiepileptic drugs are not, possibly on account of its sigma receptor activity. In addition, lamotrigine shares few side effects with other, unrelated anticonvulsants known to inhibit sodium channels, which further emphasizes its unique properties.

It is a triazine derivate that inhibits voltage-sensitive sodium channels, leading to stabilisation of neuronal membranes. It also blocks L-, N-, and P-type calcium channels and weakly inhibits the serotonin 5-HT3 receptor. These actions are thought to inhibit release of glutamate at cortical projections in the ventral striatum limbic areas, and its neuroprotective and anti-glutamatergic effects have been pointed out as promising contributors to its mood stabilising activity. Observations that lamotrigine reduced γ-aminobutyric acid (GABA) A receptor-mediated neurotransmission in rat amygdala, suggest that a GABAergic mechanism may also be involved. It appears that lamotrigine does not increase GABA blood levels in humans.

Lamotrigine does not have pronounced effects on any of the usual neurotransmitter receptors that anticonvulsants affect (adrenergic, dopamine D1 and D2, muscarinic, GABA, histaminergic H1, serotonin 5-HT2, and N-methyl-D-aspartate). Inhibitory effects on 5-HT, norepinephrine, and dopamine transporters are weak. Lamotrigine is a weak inhibitor of dihydrofolate reductase, but whether this effect is sufficient to contribute to a mechanism of action or increases risk to the foetus during pregnancy is not known. Early studies of lamotrigine’s mechanism of action examined its effects on the release of endogenous amino acids from rat cerebral cortex slices in vitro. As is the case for antiepileptic drugs that act on voltage-dependent sodium channels, lamotrigine thereby inhibits the release of glutamate and aspartate, which is evoked by the sodium-channel activator veratrine, and was less effective in the inhibition of acetylcholine or GABA release. At high concentrations, it had no effect on spontaneous or potassium-evoked amino acid release.

These studies suggested that lamotrigine acts presynaptically on voltage-gated sodium channels to decrease glutamate release. Several electrophysiological studies have investigated the effects of lamotrigine on voltage-gated sodium channels. For example, lamotrigine blocked sustained repetitive firing in cultured mouse spinal cord neurons in a concentration-dependent manner, at concentrations that are therapeutically relevant in the treatment of human seizures. In cultured hippocampal neurons, lamotrigine reduced sodium currents in a voltage-dependent manner, and at depolarised potentials showed a small frequency-dependent inhibition. These and a variety of other results indicate that the antiepileptic effect of lamotrigine, like those of phenytoin and carbamazepine, is at least in part due to use- and voltage-dependent modulation of fast voltage-dependent sodium currents. However, lamotrigine has a broader clinical spectrum of activity than phenytoin and carbamazepine and is recognised to be protective against generalised absence epilepsy and other generalised epilepsy syndromes, including primary generalised tonic-clonic seizures, juvenile myoclonic epilepsy, and Lennox-Gastaut syndrome.

The basis for this broader spectrum of activity of lamotrigine is unknown, but could relate to actions of the drug on voltage-gated calcium channels. Lamotrigine blocks T-type calcium channels weakly, if at all. However, it does inhibit native and recombinant high voltage–gated calcium channels (N- and P/Q/R-types) at therapeutic concentrations. Whether this activity on calcium channels accounts for lamotrigine’s broader clinical spectrum of activity in comparison with phenytoin and carbamazepine remains to be determined.

It antagonises these receptors with the following IC50 values:

  • 5-HT3, IC50 = 18 μM
  • σ receptors, IC50 = 145 μM

Pharmacokinetics

The pharmacokinetics of lamotrigine follow first-order kinetics, with a half-life of 29 hours and volume of distribution of 1.36 L/kg. Lamotrigine is rapidly and completely absorbed after oral administration. Its absolute bioavailability is 98% and its plasma Cmax occurs from 1.4 to 4.8 hours. Available data indicate that its bioavailability is not affected by food. Estimate of the mean apparent volume of distribution of lamotrigine following oral administration ranges from 0.9 to 1.3 L/kg. This is independent of dose and is similar following single and multiple doses in both patients with epilepsy and in healthy volunteers.

Lamotrigine is inactivated by glucuronidation in the liver. Lamotrigine is metabolised predominantly by glucuronic acid conjugation. Its major metabolite is an inactive 2-n-glucuronide conjugate.

Lamotrigine has fewer drug interactions than many anticonvulsant drugs, although pharmacokinetic interactions with carbamazepine, phenytoin and other hepatic enzyme inducing medications may shorten half-life. Dose adjustments should be made on clinical response, but monitoring may be of benefit in assessing compliance.

The capacity of available tests to detect potentially adverse consequences of melanin binding is unknown. Clinical trials excluded subtle effects and optimal duration of treatment. There are no specific recommendations for periodic ophthalmological monitoring. Lamotrigine binds to the eye and melanin-containing tissues which can accumulate over time and may cause toxicity. Prescribers should be aware of the possibility of long-term ophthalmologic effects and base treatment on clinical response. Patient compliance should be periodically reassessed with lab and medical testing of liver and kidney function to monitor progress or side effects.

Society and Culture

Brand Names

Lamotrigine was originally brought to market by GlaxoSmithKline, trademarked as Lamictal; it is also available in generic form under many brand names worldwide.

What is Flunitrazepam?

Published on by Andrew Marshall5 Comments

Introduction

Flunitrazepam, also known as Rohypnol among other names, is a benzodiazepine used to treat severe insomnia and assist with anaesthesia.

As with other hypnotics, flunitrazepam has been advised to be prescribed only for short-term use or by those with chronic insomnia on an occasional basis. It is said to be 10 times as potent as diazepam.

It was patented in 1962 and came into medical use in 1974. Flunitrazepam, nicknamed “roofies”, is widely known for its use as a date rape drug.

Brief History

Flunitrazepam was discovered at Roche as part of the benzodiazepine work led by Leo Sternbach; the patent application was filed in 1962 and it was first marketed in 1974.

Due to use of the drug for date rape and recreation, in 1998 Roche modified the formulation to give lower doses, make it less soluble, and add a blue dye for easier detection in drinks. It was never marketed in the United States, and by 2016 had been withdrawn from the markets in Spain, France, Norway, Germany, and the United Kingdom.

Use

In countries where this drug is used, it is used for treatment of severe cases of sleeping problems, and in some countries as a preanesthetic agent. These were also the uses for which it was originally studied.

It has also been administered as a concurrent dose for patients that are taking ketamine. Rohypnol lowers the side effects of the anaesthetic (ketamine), resulting in less confusion in awakening states, less negative influence on pulse rate, and fewer fluctuations in blood pressure.

It has also been shown to have therapeutic use in polysubstance use when combined with anaesthetics, opioids, ethanol, cocaine, and methamphetamine.

Adverse Effects

Adverse effects of flunitrazepam include dependency, both physical and psychological; reduced sleep quality resulting in somnolence; and overdose, resulting in excessive sedation, impairment of balance and speech, respiratory depression or coma, and possibly death. Because of the latter, flunitrazepam is commonly used in suicide. When used in late pregnancy, it might cause hypotonia of the foetus.

Dependence

Flunitrazepam, as with other benzodiazepines, can lead to drug dependence. Discontinuation may result in benzodiazepine withdrawal syndrome, characterised by seizures, psychosis, insomnia, and anxiety. Rebound insomnia, worse than baseline insomnia, typically occurs after discontinuation of flunitrazepam even from short-term single nightly dose therapy.

Paradoxical Effects

Flunitrazepam may cause a paradoxical reaction in some individuals, including anxiety, aggressiveness, agitation, confusion, disinhibition, loss of impulse control, talkativeness, violent behaviour, and even convulsions. Paradoxical adverse effects may even lead to criminal behaviour.

Hypotonia

Benzodiazepines such as flunitrazepam are lipophilic and rapidly penetrate membranes and, therefore, rapidly cross over into the placenta with significant uptake of the drug. Use of benzodiazepines including flunitrazepam in late pregnancy, especially high doses, may result in hypotonia, also known as floppy baby syndrome.

Other

Flunitrazepam impairs cognitive functions. This may appear as lack of concentration, confusion and anterograde amnesia – the inability to create memories while under the influence. It can be described as a hangover-like effect which can persist to the next day. It also impairs psychomotor functions similar to other benzodiazepines and nonbenzodiazepine hypnotic drugs; falls and hip fractures were frequently reported. The combination with alcohol increases these impairments. Partial, but incomplete tolerance develops to these impairments.

Other adverse effects include:

  • Slurred speech.
  • Gastrointestinal disturbances, lasting 12 or more hours.
  • Vomiting.
  • Respiratory depression in higher doses.

Special Precautions

Benzodiazepines require special precaution if used in the elderly, during pregnancy, in children, in alcohol- or drug-dependent individuals, and in individuals with comorbid psychiatric disorders.

Impairment of driving skills with a resultant increased risk of road traffic accidents is probably the most important adverse effect. This side-effect is not unique to flunitrazepam but also occurs with other hypnotic drugs. Flunitrazepam seems to have a particularly high risk of road traffic accidents compared to other hypnotic drugs. Extreme caution should be exercised by drivers after taking flunitrazepam.

Interactions

The use of flunitrazepam in combination with alcoholic beverages synergizes the adverse effects, and can lead to toxicity and death.

Overdose

Refer to Benzodiazepine Overdose.

Flunitrazepam is a drug that is frequently involved in drug intoxication, including overdose. Overdose of flunitrazepam may result in excessive sedation, or impairment of balance or speech. This may progress in severe overdoses to respiratory depression or coma and possibly death. The risk of overdose is increased if flunitrazepam is taken in combination with CNS depressants such as ethanol (alcohol) and opioids. Flunitrazepam overdose responds to the GABAA receptor antagonist flumazenil, which thus can be used as a treatment.

Detection

As of 2016, blood tests can identify flunitrazepam at concentrations of as low as 4 nanograms per millilitre; the elimination half life of the drug is 11-25 hours. For urine samples, metabolites can be identified for 60 hours to 28 days, depending on the dose and analytical method used. Hair and saliva can also be analysed; hair is useful when a long time has transpired since ingestion, and saliva for workplace drug tests.

Flunitrazepam can be measured in blood or plasma to confirm a diagnosis of poisoning in hospitalised patients, provide evidence in an impaired driving arrest, or assist in a medicolegal death investigation. Blood or plasma flunitrazepam concentrations are usually in a range of 5-20 μg/L in persons receiving the drug therapeutically as a nighttime hypnotic, 10-50 μg/L in those arrested for impaired driving and 100-1000 μg/L in victims of acute fatal overdosage. Urine is often the preferred specimen for routine substance use monitoring purposes. The presence of 7-aminoflunitrazepam, a pharmacologically-active metabolite and in vitro degradation product, is useful for confirmation of flunitrazepam ingestion. In postmortem specimens, the parent drug may have been entirely degraded over time to 7-aminoflunitrazepam. Other metabolites include desmethylflunitrazepam and 3-hydroxydesmethylflunitrazepam.

Pharmacology

The main pharmacological effects of flunitrazepam are the enhancement of GABA, an inhibitory neurotransmitter, at various GABA receptors.

While 80% of flunitrazepam that is taken orally is absorbed, bioavailability in suppository form is closer to 50%.

Flunitrazepam has a long half-life of 18-26 hours, which means that flunitrazepam’s effects after nighttime administration persist throughout the next day. This is due to the production of active metabolites. These metabolites further increase the duration of drug action compared to benzodiazepines that produce nonactive metabolites.

Flunitrazepam is lipophilic and is metabolised by the liver via oxidative pathways. The enzyme CYP3A4 is the main enzyme in its phase 1 metabolism in human liver microsomes.

Chemistry

Flunitrazepam is classed as a nitro-benzodiazepine. It is the fluorinated N-methyl derivative of nitrazepam. Other nitro-benzodiazepines include nitrazepam (the parent compound), nimetazepam (methylamino derivative) and clonazepam (2ʹ-chlorinated derivative).

Society and Culture

Recreational and Illegal Uses

Recreational Use

A 1989 article in the European Journal of Clinical Pharmacology reports that benzodiazepines accounted for 52% of prescription forgeries, suggesting that benzodiazepines was a major prescription drug class of abuse. Nitrazepam accounted for 13% of forged prescriptions.

Flunitrazepam and other sedative hypnotic drugs are detected frequently in cases of people suspected of driving under the influence of drugs. Other benzodiazepines and nonbenzodiazepines (anxiolytic or hypnotic) such as zolpidem and zopiclone (as well as cyclopyrrolones, imidazopyridines, and pyrazolopyrimidines) are also found in high numbers of suspected drugged drivers. Many drivers have blood levels far exceeding the therapeutic dose range, suggesting a high degree of potential for addiction for benzodiazepines and similar drugs.

Suicide

In studies in Sweden, flunitrazepam was the second most common drug used in suicides, being found in about 16% of cases. In a retrospective Swedish study of 1,587 deaths, in 159 cases benzodiazepines were found. In suicides when benzodiazepines were implicated, the benzodiazepines flunitrazepam and nitrazepam were occurring in significantly higher concentrations, compared to natural deaths. In 4 of the 159 cases, where benzodiazepines were found, benzodiazepines alone were the only cause of death. It was concluded that flunitrazepam and nitrazepam might be more toxic than other benzodiazepines.

Drug-Facilitated Sexual Assault

Flunitrazepam is known to induce anterograde amnesia in sufficient doses; individuals are unable to remember certain events that they experienced while under the influence of the drug, which complicates investigations. This effect could be particularly dangerous if flunitrazepam is used to aid in the commission of sexual assault; victims may be unable to clearly recall the assault, the assailant, or the events surrounding the assault.

While use of flunitrazepam in sexual assault has been prominent in the media, as of 2015 appears to be fairly rare, and use of alcohol and other benzodiazepine drugs in date rape appears to be a larger but underreported problem.

Drug-Facilitated Robbery

In the United Kingdom, the use of flunitrazepam and other “date rape” drugs have also been connected to stealing from sedated victims. An activist quoted by a British newspaper estimated that up to 2,000 individuals are robbed each year after being spiked with powerful sedatives, making drug-assisted robbery a more commonly reported problem than drug-assisted rape.

Regional Use

Flunitrazepam is a Schedule III drug under the international Convention on Psychotropic Substances of 1971.

  • In Australia, as of 2013 the drug was authorised for prescribing for severe cases of insomnia but was restricted as a Schedule 8 medicine.
  • In France, as of 2016 flunitrazepam was not marketed.
  • In Germany, as of 2016 flunitrazepam is an Anlage III Betäubungsmittel (controlled substance which is allowed to be marketed and prescribed by physicians under specific provisions) and is available on a special narcotic drug prescription as the Rohypnol 1 mg film-coated tablets and several generic preparations (November 2016).
  • In Ireland, flunitrazepam is a Schedule 3 controlled substance with strict restrictions.
  • In Japan, flunitrazepam is marketed by Japanese pharmaceutical company Chugai under the trade name Rohypnol and is indicated for the treatment of insomnia as well as used for preanesthetic medication.
  • In Mexico, Rohypnol is legally available and approved for medical use.
  • In Norway, on 01 January 2003, flunitrazepam was moved up one level in the schedule of controlled drugs and, on 01 August 2004, the manufacturer Roche removed Rohypnol from the market there altogether.
  • In South Africa, Rohypnol is classified as a Schedule 6 drug. It is available by prescription only, and restricted to 1 mg doses.
  • In Iceland, Flunitrazepam is a controlled substance available from Mylan. It is prescribed for severe insomnia and is sometimes used before surgery to induce a calm, relaxed state of mind for the patient.
  • In Sweden, flunitrazepam was previously available from Mylan, but has been removed from the market in January 2020. It is listed as a List II (Schedule II) under the Narcotics Control Act (1968).
  • In the United Kingdom, flunitrazepam is not licensed for medical use and is a controlled drug under Schedule 3 and Class C.
  • In the United States, the drug has not been approved by the Food and Drug Administration and is considered to be an illegal drug; as of 2016 it is Schedule IV. 21 U.S.C. § 841 and 21 U.S.C. § 952 provide for punishment for the importation and distribution of up to 20 years in prison and a fine; possession is punishable by three years and a fine. Travelers travelling into the United States are limited to a 30-day supply. The drug must be declared to US Customs upon arrival. If a valid prescription cannot be produced, the drug may be subject to Customs search and seizure, and the traveller may face criminal charges or deportation.

Names

Flunitrazepam is marketed under many brand names in the countries where it is legal. It also has many street names, including “roofie” and “ruffie”. It is also known as Circles, Forget Me Pill, La Rocha, Lunch Money Drug, Mexican Valium, Pingus, R2, and Roach 2.

What is Carbamazepine?

Published on by Andrew Marshall26 Comments

Introduction

Carbamazepine (CBZ), sold under the trade name Tegretol among others, is an anticonvulsant medication used primarily in the treatment of epilepsy and neuropathic pain.

It is used as an adjunctive treatment in schizophrenia along with other medications and as a second-line agent in bipolar disorder. Carbamazepine appears to work as well as phenytoin and valproate for focal and generalised seizures. It is not effective for absence or myoclonic seizures.

Common side effects include nausea and drowsiness. Serious side effects may include skin rashes, decreased bone marrow function, suicidal thoughts, or confusion. It should not be used in those with a history of bone marrow problems. Use during pregnancy may cause harm to the baby; however, stopping the medication in pregnant women with seizures is not recommended. Its use during breastfeeding is not recommended. Care should be taken in those with either kidney or liver problems.

Carbamazepine was discovered in 1953 by Swiss chemist Walter Schindler. It was first marketed in 1962. It is available as a generic medication. It is on the World Health Organisation’s List of Essential Medicines. In 2018, it was the 204th most commonly prescribed medication in the United States, with more than 2 million prescriptions. The newer but structurally related drugs, Oxcarbazepine and eslicarbazepine acetate, both show similar interactions, adverse events, and mechanism of action profiles.

Brief History

Carbamazepine was discovered by chemist Walter Schindler at J.R. Geigy AG (now part of Novartis) in Basel, Switzerland, in 1953. It was first marketed as a drug to treat epilepsy in Switzerland in 1963 under the brand name “Tegretol”; its use for trigeminal neuralgia (formerly known as tic douloureux) was introduced at the same time. It has been used as an anticonvulsant and antiepileptic in the UK since 1965, and has been approved in the US since 1968.

In 1971, Drs. Takezaki and Hanaoka first used carbamazepine to control mania in patients refractory to antipsychotics (lithium was not available in Japan at that time). Dr. Okuma, working independently, did the same thing with success. As they were also epileptologists, they had some familiarity with the anti-aggression effects of this drug. Carbamazepine was studied for bipolar disorder throughout the 1970s.

Medical Uses

Carbamazepine is typically used for the treatment of seizure disorders and neuropathic pain. It is used off-label as a second-line treatment for bipolar disorder and in combination with an antipsychotic in some cases of schizophrenia when treatment with a conventional antipsychotic alone has failed. However, evidence does not support this usage. It is not effective for absence seizures or myoclonic seizures. Although carbamazepine may have a similar effectiveness (people continue on medication) and efficacy (medicine reduces seizure recurrence and improves remission) when compared to phenytoin and valproate the choice of medications should be considered for each person individually as further research is needed to determine which medication is most helpful for people with newly-onset seizures.

In the United States, the FDA-approved medical uses are epilepsy (including partial seizures, generalised tonic-clonic seizures and mixed seizures), trigeminal neuralgia, and manic and mixed episodes of bipolar I disorder.

The drug is also claimed to be effective for ADHD.

As of 2014, a controlled release formulation was available for which there is tentative evidence showing fewer side effects and unclear evidence with regard to whether there is a difference in efficacy.

Adverse Effects

In the US, the label for carbamazepine contains warnings concerning:

  • Effects on the body’s production of red blood cells, white blood cells, and platelets: rarely, there are major effects of aplastic anaemia and agranulocytosis reported and more commonly, there are minor changes such as decreased white blood cell or platelet counts, but these do not progress to more serious problems.
  • Increased risks of suicide.
  • Increased risks of hyponatremia and syndrome of inappropriate antidiuretic hormone secretion (SIADH).
  • Risk of seizures, if the person stops taking the drug abruptly.
  • Risks to the foetus in women who are pregnant, specifically congenital malformations like spina bifida, and developmental disorders.

Common adverse effects may include drowsiness, dizziness, headaches and migraines, motor coordination impairment, nausea, vomiting, and/or constipation. Alcohol use while taking carbamazepine may lead to enhanced depression of the central nervous system.[2] Less common side effects may include increased risk of seizures in people with mixed seizure disorders,[21] abnormal heart rhythms, blurry or double vision.[2] Also, rare case reports of an auditory side effect have been made, whereby patients perceive sounds about a semitone lower than previously; this unusual side effect is usually not noticed by most people, and disappears after the person stops taking carbamazepine.

Pharmacogenetics

Serious skin reactions such as Stevens–Johnson syndrome or toxic epidermal necrolysis due to carbamazepine therapy are more common in people with a particular human leukocyte antigen allele, HLA-B1502. Odds ratios for the development of Stevens-Johnson syndrome or toxic epidermal necrolysis (SJS/TEN) in people who carry the allele can be in the double, triple or even quadruple digits, depending on the population studied. HLA-B1502 occurs almost exclusively in people with ancestry across broad areas of Asia, but has a very low or absent frequency in European, Japanese, Korean and African populations. However, the HLA-A31:01 allele has been shown to be a strong predictor of both mild and severe adverse reactions, such as the DRESS form of severe cutaneous reactions, to carbamazepine among Japanese, Chinese, Korean, and Europeans. It is suggested that carbamazepine acts as a potent antigen that binds to the antigen-presenting area of HLA-B1502 alike, triggering an everlasting activation signal on immature CD8-T cells, thus resulting in widespread cytotoxic reactions like SJS/TEN.

Interactions

Carbamazepine has a potential for drug interactions. Drugs that decrease breaking down of carbamazepine or otherwise increase its levels include erythromycin, cimetidine, propoxyphene, and calcium channel blockers. Grapefruit juice raises the bioavailability of carbamazepine by inhibiting the enzyme CYP3A4 in the gut wall and in the liver. Lower levels of carbamazepine are seen when administrated with phenobarbital, phenytoin, or primidone, which can result in breakthrough seizure activity.

Valproic acid and valnoctamide both inhibit microsomal epoxide hydrolase (mEH), the enzyme responsible for the breakdown of the active metabolite carbamazepine-10,11-epoxide into inactive metabolites. By inhibiting mEH, valproic acid and valnoctamide cause a build-up of the active metabolite, prolonging the effects of carbamazepine and delaying its excretion.

Carbamazepine, as an inducer of cytochrome P450 enzymes, may increase clearance of many drugs, decreasing their concentration in the blood to subtherapeutic levels and reducing their desired effects. Drugs that are more rapidly metabolized with carbamazepine include warfarin, lamotrigine, phenytoin, theophylline, valproic acid, many benzodiazepines, and methadone. Carbamazepine also increases the metabolism of the hormones in birth control pills and can reduce their effectiveness, potentially leading to unexpected pregnancies.

Pharmacology

Mechanism of Action

Carbamazepine is a sodium channel blocker. It binds preferentially to voltage-gated sodium channels in their inactive conformation, which prevents repetitive and sustained firing of an action potential. Carbamazepine has effects on serotonin systems but the relevance to its anti-seizure effects is uncertain. There is evidence that it is a serotonin releasing agent and possibly even a serotonin reuptake inhibitor.

Pharmacokinetics

Carbamazepine is relatively slowly but practically completely absorbed after administration by mouth. Highest concentrations in the blood plasma are reached after 4 to 24 hours depending on the dosage form. Slow release tablets result in about 15% lower absorption and 25% lower peak plasma concentrations than ordinary tablets, as well as in less fluctuation of the concentration, but not in significantly lower minimum concentrations.

20 to 30% of the substance are circulating in form of carbamazepine itself, the rest are metabolites. 70 to 80% are bound to plasma proteins. Concentrations in the breast milk are 25 to 60% of those in the blood plasma.

Carbamazepine itself is not pharmacologically active. It is activated, mainly by CYP3A4, to carbamazepine-10,11-epoxide, which is solely responsible for the drug’s anticonvulsant effects. The epoxide is then inactivated by microsomal epoxide hydrolase (mEH) to carbamazepine-trans-10,11-diol and further to its glucuronides. Other metabolites include various hydroxyl derivatives and carbamazepine-N-glucuronide.

The plasma half-life is about 35 to 40 hours when carbamazepine is given as single dose, but it is a strong inducer of liver enzymes, and the plasma half-life shortens to about 12 to 17 hours when it is given repeatedly. The half-life can be further shortened to 9-10 hours by other enzyme inducers such as phenytoin or phenobarbital. About 70% are excreted via the urine, almost exclusively in form of its metabolites, and 30% via the faeces.

Society and Culture

Environmental Impact

Carbamazepine and its (bio-)transformation products have been detected in wastewater treatment plant effluent  and in streams receiving treated wastewater. Field and laboratory studies have been conducted to understand the accumulation of carbamazepine in food plants grown in soil treated with sludge, which vary with respect to the concentrations of carbamazepine present in sludge and in the concentrations of sludge in the soil. Taking into account only studies that used concentrations commonly found in the environment, a 2014 review concluded that “the accumulation of carbamazepine into plants grown in soil amended with biosolids poses a de minimis risk to human health according to the approach.” 

Brand Names

Carbamazepine is available worldwide under many brand names including Tegretol.

What is Bretazenil?

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Introduction

Bretazenil (Ro16-6028) is an imidazopyrrolobenzodiazepine anxiolytic drug which is derived from the benzodiazepine family, and was invented in 1988.

It is most closely related in structure to the GABA antagonist flumazenil, although its effects are somewhat different. It is classified as a high-potency benzodiazepine due to its high affinity binding to benzodiazepine binding sites where it acts as a partial agonist. Its profile as a partial agonist and preclinical trial data suggests that it may have a reduced adverse effect profile. In particular bretazenil has been proposed to cause a less strong development of tolerance and withdrawal syndrome. Bretazenil differs from traditional 1,4-benzodiazepines by being a partial agonist and because it binds to α1, α2, α3, α4, α5 and α6 subunit containing GABAA receptor benzodiazepine receptor complexes. 1,4-benzodiazepines bind only to α1, α2, α3 and α5 GABAA benzodiazepine receptor complexes.

Brief History

Bretazenil was originally developed as an anti-anxiety drug and has been studied for its use as an anticonvulsant but has never commercialised. It is a partial agonist for GABAA receptors in the brain. David Nutt from the University of Bristol has suggested bretazenil as a possible base from which to make a better social drug, as it displays several of the positive effects of alcohol intoxication such as relaxation and sociability, but without the bad effects such as aggression, amnesia, nausea, loss of coordination, liver disease and brain damage. The effects of bretazenil can also be quickly reversed by the action of flumazenil, which is used as an antidote to benzodiazepine overdose, in contrast to alcohol for which there is no effective and reliable antidote.

Traditional benzodiazepines are associated with side effects such as drowsiness, physical dependence and abuse potential. It was hoped that bretazenil and other partial agonists would be an improvement on traditional benzodiazepines which are full agonists due to preclinical evidence that their side effect profile was less than that of full agonist benzodiazepines. For a variety of reasons however, bretazenil and other partial agonists such as pazinaclone and abecarnil were not clinically successful. However, research continues into other compounds with partial agonist and compounds which are selective for certain GABAA benzodiazepine receptor subtypes.

Tolerance and Dependence

In a study in rats, cross-tolerance between the benzodiazepine drug chlordiazepoxide and bretazenil has been demonstrated. In a primate study bretazenil was found to be able to replace the full agonist diazepam in diazepam dependent primates without precipitating withdrawal effects, demonstrating cross tolerance between bretazenil and benzodiazepine agonists, whereas other partial agonists precipitated a withdrawal syndrome. The differences are likely due to differences in intrinsic properties between different benzodiazepine partial agonists. Cross-tolerance has also been shown between bretazenil and full agonist benzodiazepines in rats. In rats tolerance is slower to develop to the anticonvulsant effects compared to the benzodiazepine site full agonist diazepam. However, tolerance developed to the anticonvulsant effects of bretazenil partial agonist more quickly than they developed to imidazenil.

Pharmacology

Bretazenil has a more broad spectrum of action than traditional benzodiazepines as it has been shown to have low affinity binding to α4 and α6 GABAA receptors in addition to acting on α1, α2, α3 and α5 subunits which traditional benzodiazepine drugs work on. The partial agonist imidazenil does not, however, act at these subunits. 0.5mg of bretazenil is approximately equivalent in its psychomotor-impairing effect to 10 mg of diazepam. Bretazenil produces marked sedative-hypnotic effects when taken alone and when combined with alcohol. This human study also indicates that bretazenil is possibly more sedative than diazepam. The reason is unknown, but the study suggests the possibility that a full-agonist metabolite may be generated in humans but not animals previously tested or else that there are significant differences in benzodiazepine receptor population in animals and humans.

In a study of monkeys bretazenil has been found to antagonize the effects of full agonist benzodiazepines. However, bretazenil has been found to enhance the effects of neurosteroids acting on the neurosteroid binding site of the GABAA receptor. Another study found that bretazenil acted as an antagonist provoking withdrawal symptoms in monkeys who were physically dependent on the full agonist benzodiazepine triazolam.

Partial agonists of benzodiazepine receptors have been proposed as a possible alternative to full agonists of the benzodiazepine site to overcome the problems of tolerance, dependence and withdrawal which limits the role of benzodiazepines in the treatment of anxiety, insomnia and epilepsy. Such adverse effects appear to be less problematic with bretazenil than full agonists. Bretazenil has also been found to have less abuse potential than benzodiazepine full agonists such as diazepam and alprazolam, however long-term use of bretazenil would still be expected to result in dependence and addiction.

Bretazenil alters the sleep EEG profile and causes a reduction in cortisol secretion and increases significantly the release of prolactin. Bretazenil has effective hypnotic properties but impairs cognitive ability in humans. Bretazenil causes a reduction in the number of movements between sleep stages and delays movement into REM sleep. At a dosage of 0.5 mg of bretazenil REM sleep is decreased and stage 2 sleep is lengthened.

What is Reboxetine?

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Introduction

Reboxetine, sold under the brand name Edronax among others, is a drug of the norepinephrine reuptake inhibitor (NRI) class, marketed as an antidepressant by Pfizer for use in the treatment of major depression, although it has also been used off-label for panic disorder and attention deficit hyperactivity disorder (ADHD).

It is approved for use in many countries worldwide, but has not been approved for use in the United States. Although its effectiveness as an antidepressant has been challenged in multiple published reports, its popularity has continued to increase.

Brief History

Reboxetine was discovered at Farmitalia-Carlo Erba and was first published in 1984; Farmitalia did the first clinical studies. Farmitalia was acquired by Pharmacia in 1993, and Pharmacia in turn was acquired by Pfizer in 2003.

It was first approved in Europe in 1997 and was provisionally approved by the US Food and Drug Administration (FDA) in 1999. In 2001 the FDA issued Pfizer a “not approvable” letter based on clinical trials the FDA had required when it issued the preliminary approval letter.

In 2010, the German Institute for Quality and Efficiency in Health Care (IQEHC) published results of a meta-analysis of clinical trial data for reboxetine in acute depression, which included data on about 3,000 subjects that Pfizer had never published but had mentioned; IQEHC had combed through Pfizer’s publications and reboxetine approvals and had determined this data was missing from the publication record. The analysis of the complete data set yielded a result that reboxetine was not more effective than placebo but had more side effects than placebo and more than fluoxetine; the paper led to widespread and sharp criticism of Pfizer, and stronger calls for publication of all clinical trial data.

Medical Uses

Major Depressive Disorder

There has been much debate as to whether reboxetine is more efficacious than placebo in the treatment of depression. According to a 2009 meta-analysis of 12 second-generation antidepressants, reboxetine was no more effective than placebo, and was “significantly less” effective, and less acceptable, than the other drugs in treating the acute-phase of adults with unipolar major depression.

The UK’s Medicines and Healthcare Products Regulatory Agency (MHRA) said in September 2011 that the study had several limitations, and that “Overall the balance of benefits and risks for reboxetine remains positive in its authorised indication.” A UK and Europe-wide review of available efficacy and safety data has confirmed that reboxetine has benefit over placebo in its authorised indication. Efficacy was clearly shown in patients with severe or very severe depression.

According to a systematic review and meta-analysis by IQWiG, including unpublished data, published data on reboxetine overestimated the benefit of reboxetine versus placebo by up to 115% and reboxetine versus SSRIs by up to 23%, and also underestimated harm, concluding that reboxetine was an ineffective and potentially harmful antidepressant. The study also showed that nearly three quarters of the data on patients who took part in trials of reboxetine had not been published by Pfizer.

A 2018 systematic review and network meta-analysis comparing the efficacy and acceptability of 21 antidepressant drugs concluded that reboxetine was significantly less efficacious than other antidepressants tested.

Panic Disorder

In a randomised double-blind placebo-controlled trial reboxetine significantly improved the symptoms of panic disorder. Another randomised controlled trial that compared paroxetine to reboxetine found that paroxetine significantly outperformed reboxetine as a treatment for panic disorder. Despite this discouraging finding an open-label trial examining the efficacy of reboxetine in SSRI-resistant panic disorder demonstrated significant benefit from reboxetine treatment.

Attention Deficit Hyperactivity Disorder

Numerous clinical trials have provided support for the efficacy of reboxetine in the treatment of attention deficit hyperactivity disorder (ADHD) in both the short and long-term and in both children/adolescents and adults.

Other Uses

A case series and open-label pilot study demonstrated the efficacy of reboxetine in treating bulimia nervosa. Reboxetine may also have efficacy in treating therapy-resistant paediatric nocturnal enuresis. A pilot study demonstrated the efficacy of reboxetine in the treatment of narcolepsy. Individual trials and meta-analysis suggest that reboxetine can attenuate antipsychotic-induced weight gain and there is some evidence of a benefit on depressive, and possibly other symptoms of schizophrenia when added to antipsychotic treatment.

Contraindications

Reboxetine is contraindicated in narrow-angle glaucoma, cardiovascular disease, epilepsy, bipolar disorder, urinary retention, prostatic hypertrophy, patients concomitantly on MAOIs and those hypersensitive to reboxetine or any of its excipients.

Adverse Effects

Very common (>10% incidence) adverse effects include insomnia, dizziness, dry mouth, constipation, nausea, and excessive sweating.

Common (1-10%) adverse effects include loss of appetite, agitation, anxiety, headache, restlessness, tingling sensations, distorted sense of taste, difficulty with seeing near or far (problems with accommodation), fast heart beat, heart palpitations, relaxing of blood vessels leading to low blood pressure, high blood pressure, vomiting, rash, sensation of incomplete bladder emptying, urinary tract infection, painful or difficult urination, urinary retention, erectile dysfunction, ejaculatory pain or delay, and chills.

A 2009 meta-analysis found that reboxetine was significantly less well tolerated than the other 11 second-generation antidepressants compared in the analysis

Overdose

Reboxetine is considered a relatively low-risk antidepressant in overdose.[26] The symptoms are as follows:

  • Sweating.
  • Tachycardia.
  • Changes in blood pressure.

Interactions

Because of its reliance on CYP3A4, reboxetine O-desethylation is markedly inhibited by papaverine and ketoconazole. It weakly inhibits CYP2D6 and CYP3A4.[25] Reboxetine is an intermediate-level inhibitor of P-glycoprotein, which gives it the potential to interact with ciclosporin, tacrolimus, paroxetine, sertraline, quinidine, fluoxetine, fluvoxamine.

Pharmacology

Pharmacodynamics

Reboxetine is a fairly selective norepinephrine reuptake inhibitor (NRI), with approximately 20-fold selectivity for the norepinephrine transporter (NET) over the serotonin transporter (SERT). Despite this selectivity, reboxetine does slightly inhibit the reuptake of serotonin at therapeutic doses. It does not interact with or inhibit the dopamine transporter (DAT).

Reboxetine has been found to inhibit both brain and cardiac GIRKs, a characteristic it shares with the NRI atomoxetine.

Pharmacokinetics

Both the (R,R)-(–) and (S,S)-(+)-enantiomers of reboxetine are predominantly metabolised by the CYP3A4 isoenzyme. The primary metabolite of reboxetine is O-desethylreboxetine, and there are also three minor metabolites – Phenol A, Phenol B, and UK1, Phenol B being the most minor

Chemistry

Reboxetine has two chiral centres. Thus, four stereoisomers may exist, the (R,R)-, (S,S)-, (R,S)-, and (S,R)-isomers. The active ingredient of reboxetine is a racemic mixture of two enantiomers, the (R,R)-(–)- and (S,S)-(+)-isomer.

Society and Culture

Brand Names

Edronax is the brand name of reboxetine in every English-speaking country that has approved it for clinical use. Brand names include (where † denotes a product that is no longer marketed):

  • Davedax (IT).
  • Edronax (AU, AT, BE, CZ, DK, FI, DE, IE, IL, IT, MX, NZ, NO, PH, PL, PT, ZA, SE, CH, TH, TR, UK).
  • Irenor (ES).
  • Norebox (ES).
  • Prolift (AR,† BR, CL, VE†).
  • Solvex (DE).
  • Yeluoshu (CN).
  • Zuolexin (CN).