What is Reboxetine?

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).

What is Flupentixol?

Introduction

Flupentixol (INN), also known as flupenthixol (former BAN), marketed under brand names such as Depixol and Fluanxol is a typical antipsychotic drug of the thioxanthene class.

It was introduced in 1965 by Lundbeck. In addition to single drug preparations, it is also available as flupentixol/melitracen – a combination product containing both melitracen (a tricyclic antidepressant) and flupentixol. Flupentixol is not approved for use in the United States. It is, however, approved for use in the UK, Australia, Canada, Russian Federation, South Africa, New Zealand, Philippines and various other countries.

Brief History

In March 1963 the Danish pharmaceutical company Lundbeck began research into further agents for schizophrenia, having already developed the thioxanthene derivatives clopenthixol and chlorprothixene. By 1965 the promising agent flupenthixol had been developed and trialled in two hospitals in Vienna by Austrian psychiatrist Heinrich Gross. The long-acting decanoate preparation was synthesised in 1967 and introduced into hospital practice in Sweden in 1968, with a reduction in relapses among patients who were put on the depot.

Medical Uses

Flupentixol’s main use is as a long-acting injection given once in every two or three weeks to individuals with schizophrenia who have poor compliance with medication and suffer frequent relapses of illness, though it is also commonly given as a tablet. There is little formal evidence to support its use for this indication but it has been in use for over fifty years.

Flupentixol is also used in low doses as an antidepressant. There is tentative evidence that it reduces the rate of deliberate self-harm, among those who self-harm repeatedly.

Adverse Effects

Common (>1% incidence) adverse effects include:

  • Extrapyramidal side effects such as (which usually become apparent soon after therapy is begun or soon after an increase in dose is made):
    • Muscle rigidity.
    • Hypokinesia.
    • Hyperkinesia.
    • Parkinsonism.
    • Tremor.
    • Akathisia.
    • Dystonia.
  • Dry mouth.
  • Constipation.
  • Hypersalivation – excessive salivation.
  • Blurred vision.
  • Diaphoresis – excessive sweating.
  • Nausea.
  • Dizziness.
  • Somnolence.
  • Restlessness.
  • Insomnia.
  • Overactivity.
  • Headache.
  • Nervousness.
  • Fatigue.
  • Myalgia.
  • Hyperprolactinemia and its complications such as: (acutely).
    • Sexual dysfunction.
    • Amenorrhea – cessation of menstrual cycles.
    • Gynecomastia – enlargement of breast tissue in males.
    • Galactorrhea – the expulsion of breast milk that’s not related to breastfeeding or pregnancy
      and if the hyperprolactinemia persists chronically, the following adverse effects may be seen:
    • Reduced bone mineral density leading to osteoporosis (brittle bones).
    • Infertility.
  • Dyspepsia – indigestion.
  • Abdominal pain.
  • Flatulence.
  • Nasal congestion.
  • Polyuria – passing more urine than usual.

Uncommon (0.1-1% incidence) adverse effects include:

  • Fainting.
  • Palpitations.

Rare (<0.1% incidence) adverse effects include:

  • Blood dyscrasias (abnormalities in the cell composition of blood), such as:
    • Agranulocytosis – a drop in white blood cell counts that leaves one open to potentially life-threatening infections.
    • Neutropenia – a drop in the number of neutrophils (white blood cells that specifically fight bacteria) in one’s blood.
    • Leucopenia – a less severe drop in white blood cell counts than agranulocytosis.
    • Thrombocytopenia – a drop in the number of platelets in the blood. Platelets are responsible for blood clotting and hence this leads to an increased risk of bruising and other bleeds.
  • Neuroleptic malignant syndrome – a potentially fatal condition that appear to result from central D2 receptor blockade. The symptoms include:
    • Hyperthermia
    • Muscle rigidity
    • Rhabdomyolysis
    • Autonomic instability (e.g. tachycardia, diarrhoea, diaphoresis, etc.).
    • Mental status changes (e.g. coma, agitation, anxiety, confusion, etc.).

Unknown incidence adverse effects include:

  • Jaundice.
  • Abnormal liver function test results.
  • Tardive dyskinesia – an often incurable movement disorder that usually results from years of continuous treatment with antipsychotic drugs, especially typical antipsychotics like flupenthixol. It presents with repetitive, involuntary, purposeless and slow movements; TD can be triggered by a fast dose reduction in any antipsychotic.
  • Hypotension.
  • Confusional state.
  • Seizures.
  • Mania.
  • Hypomania.
  • Depression.
  • Hot flush.
  • Anergia.
  • Appetite changes.
  • Weight changes.
  • Hyperglycaemia – high blood glucose (sugar) levels.
  • Abnormal glucose tolerance.
  • Pruritus – itchiness.
  • Rash.
  • Dermatitis.
  • Photosensitivity – sensitivity to light.
  • Oculogyric crisis.
  • Accommodation disorder.
  • Sleep disorder.
  • Impaired concentration.
  • Tachycardia.
  • QTc interval prolongation – an abnormality in the electrical activity of the heart that can lead to potentially fatal changes in heart rhythm (only in overdose or <10 ms increases in QTc).
  • Torsades de pointes.
  • Miosis – constriction of the pupil of the eye.
  • Paralytic ileus – paralysis of the bowel muscles leading to severe constipation, inability to pass wind, etc.
  • Mydriasis.
  • Glaucoma.

Interactions

It should not be used concomitantly with medications known to prolong the QTc interval (e.g. 5-HT3 antagonists, tricyclic antidepressants, citalopram, etc.) as this may lead to an increased risk of QTc interval prolongation. Neither should it be given concurrently with lithium (medication) as it may increase the risk of lithium toxicity and neuroleptic malignant syndrome. It should not be given concurrently with other antipsychotics due to the potential for this to increase the risk of side effects, especially neurological side effects such as neuroleptic malignant syndrome. It should be avoided in patients on CNS depressants such as opioids, alcohol and barbiturates.

Contraindications

It should not be given in the following disease states:

  • Pheochromocytoma.
  • Prolactin-dependent tumours such as pituitary prolactinomas and breast cancer.
  • Long QT syndrome.
  • Coma.
  • Circulatory collapse.
  • Subcortical brain damage.
  • Blood dyscrasia.
  • Parkinson’s disease.
  • Dementia with Lewy bodies.

What is Flupentixol/Melitracen?

Introduction

Flupentixol/melitracen (trade name Frenxit, Placida, Deanxit, Anxidreg, Danxipress) is a combination of two psychoactive agents flupentixol (a typical antipsychotic drug of the thioxanthene class) and melitracen, a tricyclic antidepressant (TCA) which has antidepressant properties.

It is designed for short term usage only. It is produced by Lundbeck.

Other Brand Names

  • Pentoxol.m (scotmann pharmaceuticals Pakistan).
  • Sensit (Eskayef Bangladesh Ltd.).
  • Renxit (Renata Ltd.).
  • Melixol (Square Pharmaceuticals Ltd.).
  • Melanxit (Organic Health Care Ltd.).
  • Benzit (Bio-Pharma Ltd.).
  • Leanxit (ACME Laboratories Ltd.).
  • Danxipress (Vickmans Lab Ltd.).
  • Amilax (Amico Lab Ltd).

What is a Psycholeptic?

Introduction

In pharmacology, a psycholeptic is a medication which produces a calming effect upon a person.

Refer to Analeptic.

Background

Such medications include barbiturates, benzodiazepines, nonbenzodiazepines, phenothiazines, opiates/opioids, carbamates, ethanol, 2-methyl-2-butanol, cannabinoids (in some classifications), some antidepressants, neuroleptics, and some anticonvulsants.

Many herbal medicines may also be classified as psycholeptics (e.g. kava).

Psycholeptics are classified under N05 in the Anatomical Therapeutic Chemical Classification System.

What is a Paradoxical Reaction?

Introduction

A paradoxical reaction or paradoxical effect is an effect of a chemical substance, typically a medical drug, that is opposite to what would usually be expected. An example of a paradoxical reaction is pain caused by a pain relief medication.

Paradoxical reactions are more commonly observed in people with attention deficit hyperactivity disorder (ADHD).

Substances

Amphetamines

Amphetamines are a class of psychoactive drugs that are stimulants. Paradoxical drowsiness can sometimes occur in adults.

Antibiotics

The paradoxical effect or Eagle effect (named after H. Eagle who first described it) refers to an observation of an increase in survivors, seen when testing the activity of an antimicrobial agent. Initially when an antibiotic agent is added to a culture media, the number of bacteria that survive drops, as one would expect. But after increasing the concentration beyond a certain point, the number of bacteria that survive, paradoxically, increases.

Antidepressants

In rare cases antidepressants can make users obsessively violent or have suicidal compulsions, which is in marked contrast to their intended effect. This can be regarded as a paradoxical reaction but, especially in the case of suicide, may in at least some cases be merely due to differing rates of effect with respect to different symptoms of depression: If generalised overinhibition of a patient’s actions enters remission before that patient’s dysphoria does and if the patient was already suicidal but too depressed to act on their inclinations, the patient may find themselves in the situation of being both still dysphoric enough to want to commit suicide but newly free of endogenous barriers against doing so. Children and adolescents are more sensitive to paradoxical reactions of self-harm and suicidal ideation while taking antidepressants but cases are still very rare.

Antipsychotics

Chlorpromazine, an antipsychotic and antiemetic drug, which is classed as a “major” tranquilizer may cause paradoxical effects such as agitation, excitement, insomnia, bizarre dreams, aggravation of psychotic symptoms and toxic confusional states.

Barbiturates

Phenobarbital can cause hyperactivity in children. This may follow after a small dose of 20 mg, on condition of no phenobarbital administered in previous days. Prerequisity for this reaction is a continued sense of tension. The mechanism of action is not known, but it may be started by the anxiolytic action of the phenobarbital.

Benzodiazepines

Benzodiazepines, a class of psychoactive drugs called the “minor” tranquilisers, have varying hypnotic, sedative, anxiolytic, anticonvulsant, and muscle relaxing properties, but they may create the exact opposite effects. Susceptible individuals may respond to benzodiazepine treatment with an increase in anxiety, aggressiveness, agitation, confusion, disinhibition, loss of impulse control, talkativeness, violent behaviour, and even convulsions. Paradoxical adverse effects may even lead to criminal behaviour. Severe behavioural changes resulting from benzodiazepines have been reported including mania, schizophrenia, anger, impulsivity, and hypomania.

Paradoxical rage reactions due to benzodiazepines occur as a result of an altered level of consciousness, which generates automatic behaviours, anterograde amnesia and uninhibited aggression. These aggressive reactions may be caused by a disinhibiting serotonergic mechanism.

Paradoxical effects of benzodiazepines appear to be dose related, that is, likelier to occur with higher doses.

In a letter to the British Medical Journal, it was reported that a high proportion of parents referred for actual or threatened child abuse were taking medication at the time, often a combination of benzodiazepines and tricyclic antidepressants. Many mothers described that instead of feeling less anxious or depressed, they became more hostile and openly aggressive towards the child as well as to other family members while consuming tranquilizers. The author warned that environmental or social stresses such as difficulty coping with a crying baby combined with the effects of tranquilisers may precipitate a child abuse event.

Self aggression has been reported and also demonstrated in laboratory conditions in a clinical study. Diazepam was found to increase people’s willingness to harm themselves.

Benzodiazepines can sometimes cause a paradoxical worsening of EEG readings in patients with seizure disorders.

Barbiturates such as pentobarbital have been shown to cause paradoxical hyperactivity in an estimated 1% of children, who display symptoms similar to the hyperactive-impulsive subtype of attention deficit hyperactivity disorder. Intravenous caffeine administration can return these patients’ behaviour to baseline levels.

Causes

The mechanism of a paradoxical reaction has as yet (2019) not been fully clarified, in no small part due to the fact that signal transfer of single neurons in subcortical areas of the human brain is usually not accessible.

There are, however, multiple indications that paradoxical reactions upon – for example – benzodiazepines, barbiturates, inhalational anaesthetics, propofol, neurosteroids, and alcohol are associated with structural deviations of GABAA receptors. The combination of the five subunits of the receptor (see image) can be altered in such a way that for example the receptor’s response to GABA remains unchanged but the response to one of the named substances is dramatically different from the normal one.

There are estimates that about 2-3% of the general population may suffer from serious emotional disorders due to such receptor deviations, with up to 20% suffering from moderate disorders of this kind. It is generally assumed that the receptor alterations are, at least partly, due to genetic and also epigenetic deviations. There are indication that the latter may be triggered by, among other factors, social stress or occupational burnout.

What is Adinazolam?

Introduction

Adinazolam (marketed under the brand name Deracyn) is a tranquiliser of the triazolobenzodiazepine (TBZD) class, which are benzodiazepines (BZDs) fused with a triazole ring.

It possesses anxiolytic, anticonvulsant, sedative, and antidepressant properties. Adinazolam was developed by Dr. Jackson B. Hester, who was seeking to enhance the antidepressant properties of alprazolam, which he also developed. Adinazolam was never approved by the US Food and Drug Administration (FDA) and never made available to the public market, however it has been sold as a designer drug.

Side Effects

Overdose may include muscle weakness, ataxia, dysarthria and particularly in children paradoxical excitement, as well as diminished reflexes, confusion and coma may ensue in more severe cases.

A human study comparing the subjective effects and abuse potential of adinazolam (30 mg and 50 mg) with diazepam, lorazepam and a placebo showed that adinazolam causes the most “mental and physical sedation” and the greatest “mental unpleasantness”.

Pharmacodynamics and Pharmacokinetics

Adinazolam binds to peripheral-type benzodiazepine receptors that interact allosterically with GABA receptors as an agonist to produce inhibitory effects.

Metabolism

Adinazolam was reported to have active metabolites in the August 1984 issue of The Journal of Pharmacy and Pharmacology. The main metabolite is N-desmethyladinazolam. NDMAD has an approximately 25-fold high affinity for benzodiazepine receptors as compared to its precursor, accounting for the benzodiazepine-like effects after oral administration. Multiple N-dealkylations lead to the removal of the dimethylaminomethyl side chain, leading to the difference in its potency. The other two metabolites are alpha-hydroxyalprazolam and estazolam. In the August 1986 issue of that same journal, Sethy, Francis and Day reported that proadifen inhibited the formation of N-desmethyladinazolam.

What is Lofepramine?

Introduction

Lofepramine, sold under the brand names Gamanil, Lomont, and Tymelyt among others, is a tricyclic antidepressant (TCA) which is used to treat depression.

The TCAs are so named as they share the common property of having three rings in their chemical structure. Like most TCAs lofepramine is believed to work in relieving depression by increasing concentrations of the neurotransmitters norepinephrine and serotonin in the synapse, by inhibiting their reuptake. It is usually considered a third-generation TCA, as unlike the first- and second-generation TCAs it is relatively safe in overdose and has milder and less frequent side effects.

Lofepramine is not available in the United States, Canada, Australia or New Zealand, although it is available in Ireland, Japan, South Africa and the United Kingdom, among other countries.

Brief History

Lofepramine was developed by Leo Läkemedel AB. It first appeared in the literature in 1969 and was patented in 1970. The drug was first introduced for the treatment of depression in either 1980 or 1983.

Depression

In the United Kingdom, lofepramine is licensed for the treatment of depression which is its primary use in medicine.

Lofepramine is an efficacious antidepressant with about 64% patients responding to it.

Contraindications

To be used with caution, or not at all, for people with the following conditions:

  • Heart disease.
  • Impaired kidney or liver function.
  • Narrow angle glaucoma.
  • In the immediate recovery period after myocardial infarction.
  • In arrhythmias (particularly heart block).
  • Mania.
  • In severe liver and/or severe renal impairment.

And in those being treated with amiodarone or terfenadine.

Pregnancy and Lactation

Lofepramine use during pregnancy is advised against unless the benefits clearly outweigh the risks. This is because its safety during pregnancy has not been established and animal studies have shown some potential for harm if used during pregnancy. If used during the third trimester of pregnancy it can cause insufficient breathing to meet oxygen requirements, agitation and withdrawal symptoms in the infant. Likewise its use by breastfeeding women is advised against, except when the benefits clearly outweigh the risks, due to the fact it is excreted in the breast milk and may therefore adversely affect the infant. Although the amount secreted in breast milk is likely too small to be harmful.

Side Effects

The most common adverse effects (occurring in at least 1% of those taking the drug) include agitation, anxiety, confusion, dizziness, irritability, abnormal sensations, like pins and needles, without a physical cause, sleep disturbances (e.g. sleeplessness) and a drop in blood pressure upon standing up. Less frequent side effects include movement disorders (like tremors), precipitation of angle closure glaucoma and the potentially fatal side effects paralytic ileus and neuroleptic malignant syndrome.

Dropout incidence due to side effects is about 20%.

Side effects with unknown frequency include (but are not limited to):

  • Digestive effects:
    • Constipation.
    • Diarrhoea.
    • Dry mouth.
    • Nausea.
    • Taste disturbances.
    • Vomiting.
  • Effects on the heart:
    • Arrhythmia.
    • ECG changes.
    • Abnormal heart rhythm.
    • Heart block.
    • Sudden cardiac death.
    • High heart rate.
  • Blood abnormalities:
    • Abnormal blood cell counts.
    • Blood sugar changes.
    • Low blood sodium levels.
  • Breast effects:
    • Breast enlargement, including in males.
    • Spontaneous breast milk secretion that is unrelated to breastfeeding or pregnancy.
  • Effects on the skin:
    • Abnormal sweating.
    • Hair loss.
    • Hives.
    • Increased light sensitivity.
    • Itching.
    • Rash.
  • Mental / neurologic effects:
    • Delusions.
    • Hallucinations.
    • Headache.
    • Hypomania/mania.
    • Seizures.
    • Suicidal behaviour.
  • Other effects:
    • Appetite changes.
    • Blurred vision.
    • Difficulty emptying the bladder.
    • Difficulty talking due to difficulties in moving the required muscles.
    • Liver problems.
    • Ringing in the ears.
    • Sexual dysfunction, such as impotence.
    • Swelling.
    • Weight changes.

Withdrawal

If abruptly stopped after regular use it can cause withdrawal effects such as sleeplessness, irritability and excessive sweating.

Overdose

Refer to Tricyclic Antidepressant Overdose.

Compared to other TCAs, lofepramine is considered to be less toxic in overdose. Its treatment is mostly a matter of trying to reduce absorption of the drug, if possible, using gastric lavage and monitoring for adverse effects on the heart.

Interactions

Lofepramine is known to interact with:

  • Alcohol. Increased sedative effect.
  • Altretamine. Risk of severe drop in blood pressure upon standing.
  • Analgesics (painkillers). Increased risk of ventricular arrhythmias.
  • Anticoagulants (blood thinners). Lofepramine may inhibit the metabolism of certain anticoagulants leading to a potentially increased risk of bleeding.
  • Anticonvulsants. Possibly reduce the anticonvulsant effect of antiepileptics by lowering the seizure threshold.
  • Antihistamines. Possible increase of antimuscarinic (potentially increasing risk of paralytic ileus, among other effects) and sedative effects.
  • Antimuscarinics. Possible increase of antimuscarinic side-effects.
  • Anxiolytics and hypnotics. Increased sedative effect.
  • Apraclonidine. Avoidance advised by manufacturer of apraclonidine.
  • Brimonidine. Avoidance advised by manufacturer of brimonidine.
  • Clonidine. Lofepramine may reduce the antihypertensive effects of clonidine.
  • Diazoxide. Enhanced hypotensive (blood pressure-lowering) effect.
  • Digoxin. May increase risk of irregular heart rate.
  • Disulfiram. May require a reduction of lofepramine dose.
  • Diuretics. Increased risk of reduced blood pressure on standing.
  • Cimetidine, diltiazem, verapamil. May increase concentration of lofepramine in the blood plasma.
  • Hydralazine. Enhanced hypotensive effect.
  • Monoamine oxidase inhibitors (MAOIs). Advised not to be started until at least 2 weeks after stopping MAOIs. MAOIs are advised not to be started until at least 1-2 weeks after stopping TCAs like lofepramine.
  • Moclobemide. Moclobemide is advised not to be started until at least one week after treatment with TCAs is discontinued.
  • Nitrates. Could possibly reduce the effects of sublingual tablets of nitrates (failure to dissolve under tongue owing to dry mouth).
  • Rifampicin. May accelerate lofepramine metabolism thereby decreasing plasma concentrations of lofepramine.
  • Ritonavir. May increase lofepramine concentration in the blood plasma.
  • Sodium nitroprusside. Enhanced hypotensive effect.
  • Thyroid hormones. Effects on the heart of lofepramine may be exacerbated.

Pharmacology

Pharmacodynamics

Lofepramine is a strong inhibitor of norepinephrine reuptake and a moderate inhibitor of serotonin reuptake. It is a weak-intermediate level antagonist of the muscarinic acetylcholine receptors.

Lofepramine has been said to be a prodrug of desipramine, although there is also evidence against this notion.

Pharmacokinetics

Lofepramine is extensively metabolised, via cleavage of the p-chlorophenacyl group, to the TCA, desipramine, in humans. However, it is unlikely this property plays a substantial role in its overall effects as lofepramine exhibits lower toxicity and anticholinergic side effects relative to desipramine while retaining equivalent antidepressant efficacy. The p-chlorophenacyl group is metabolised to p-chlorobenzoic acid which is then conjugated with glycine and excreted in the urine. The desipramine metabolite is partly secreted in the faeces. Other routes of metabolism include hydroxylation, glucuronidation, N-dealkylation and N-oxidation.

Chemistry

Lofepramine is a tricyclic compound, specifically a dibenzazepine, and possesses three rings fused together with a side chain attached in its chemical structure. Other dibenzazepine TCAs include imipramine, desipramine, clomipramine, and trimipramine. Lofepramine is a tertiary amine TCA, with its side chain-demethylated metabolite desipramine being a secondary amine. Unlike other tertiary amine TCAs, lofepramine has a bulky 4-chlorobenzoylmethyl substituent on its amine instead of a methyl group. Although lofepramine is technically a tertiary amine, it acts in large part as a prodrug of desipramine, and is more similar to secondary amine TCAs in its effects. Other secondary amine TCAs besides desipramine include nortriptyline and protriptyline. The chemical name of lofepramine is N-(4-chlorobenzoylmethyl)-3-(10,11-dihydro-5H-dibenzo[b,f]azepin-5-yl)-N-methylpropan-1-amine and its free base form has a chemical formula of C26H27ClN2O with a molecular weight of 418.958 g/mol. The drug is used commercially mostly as the hydrochloride salt; the free base form is not used. The CAS Registry Number of the free base is 23047-25-8 and of the hydrochloride is 26786-32-3.

Society and Culture

Generic Names

Lofepramine is the generic name of the drug and its INN and BAN, while lofepramine hydrochloride is its USAN, BANM, and JAN. Its generic name in French and its DCF are lofépramine, in Spanish and Italian and its DCIT are lofepramina, in German is lofepramin, and in Latin is lofepraminum.

Brand Names

Brand names of lofepramine include Amplit, Deftan, Deprimil, Emdalen, Gamanil, Gamonil, Lomont, Tymelet, and Tymelyt.

Availability

In the United Kingdom, lofepramine is marketed (as the hydrochloride salt) in the form of 70 mg tablets and 70 mg/5 mL oral suspension.

Research

Fatigue

A formulation containing lofepramine and the amino acid phenylalanine is under investigation as a treatment for fatigue as of 2015.

What is Phenelzine?

Introduction

Phenelzine, sold under the brand name Nardil, among others, is a non-selective and irreversible monoamine oxidase inhibitor (MAOI) of the hydrazine class which is used as an antidepressant and anxiolytic. Along with tranylcypromine and isocarboxazid, phenelzine is one of the few non-selective and irreversible MAOIs still in widespread clinical use. It is taken by mouth.

In June 2020, the Therapeutic Goods Administration (TGA) reported that the availability of phenelzine was discontinued in Australia due to global issues with the manufacture of the active pharmaceutical ingredient. However, unapproved phenelzine products may be accessed through alternative pathways, such as the Special Access Scheme (SAS) administered by the TGA. In October 2020, The TGA authorized two sponsors to supply an overseas-registered brand of phenelzine in Australia. In May 2020, the Specialist Pharmacy Service in the UK reported the unavailability of phenelzine from the sole supplier. In July 2020, supplies of unlicensed phenelzine 15mg capsule specials became available for UK patients. In February 2021, Phenelzine again became available in Australia as a subsidised medication through the Pharmaceutical Benefits Scheme.

Brief History

Synthesis of phenelzine was first described by Emil Votoček and Otakar Leminger in 1932.

Indications

Phenelzine is used primarily in the treatment of major depressive disorder (MDD). Patients with depressive symptomology characterised as “atypical”, “nonendogenous”, and/or “neurotic” respond particularly well to phenelzine. The medication is also useful in patients who do not respond favourably to first and second-line treatments for depression, or are “treatment-resistant”. In addition to being a recognised treatment for major depressive disorder, phenelzine is effective in treating dysthymia, bipolar depression (BD), panic disorder (PD), social anxiety disorder, bulimia, post-traumatic stress disorder (PTSD), and obsessive-compulsive disorder (OCD). Phenelzine showed promise in a phase II clinical trial from March 2020 in treating prostate cancer.

Pharmacology

Pharmacodynamics

Phenelzine is a non-selective and irreversible inhibitor of the enzyme monoamine oxidase (MAO). It inhibits both of the respective isoforms of MAO, MAO-A and MAO-B, and does so almost equally, with slight preference for the former. By inhibiting MAO, phenelzine prevents the breakdown of the monoamine neurotransmitters serotonin, melatonin, norepinephrine, epinephrine, and dopamine, as well as the trace amine neuromodulators such as phenethylamine, tyramine, octopamine, and tryptamine. This leads to an increase in the extracellular concentrations of these neurochemicals and therefore an alteration in neurochemistry and neurotransmission. This action is thought to be the primary mediator in phenelzine’s therapeutic benefits.

Phenelzine and its metabolites also inhibit at least two other enzymes to a lesser extent, of which are alanine transaminase (ALA-T), and γ-Aminobutyric acid transaminase (GABA-T), the latter of which is not caused by phenelzine itself, but by a phenelzine metabolite phenylethylidenehydrazine (PEH). By inhibiting ALA-T and GABA-T, phenelzine causes an increase in the alanine and GABA levels in the brain and body. GABA is the major inhibitory neurotransmitter in the mammalian central nervous system, and is very important for the normal suppression of anxiety, stress, and depression. Phenelzine’s action in increasing GABA concentrations may significantly contribute to its antidepressant, and especially, anxiolytic/antipanic properties, the latter of which have been considered superior to those of other antidepressants. As for ALA-T inhibition, though the consequences of disabling this enzyme are currently not well understood, there is some evidence to suggest that it is this action of the hydrazines (including phenelzine) which may be responsible for the occasional incidence of hepatitis and liver failure.

Phenelzine has also been shown to metabolise to phenethylamine (PEA). PEA acts as a releasing agent of norepinephrine and dopamine, and this occurs in the same manner as amphetamine (very similar in structure) by being taken up into vesicles, and displacing, and causing the release of those monoamines (though with markedly different pharmacokinetics such as a far shorter duration of action). Although this is indeed the same mechanism to which some (but not all) of amphetamine’s effects are attributable to, this is not all that uncommon a property among phenethylamines in general, many of which do not have psychoactive properties comparable to amphetamine. Amphetamine is different in that it binds with high affinity to the reuptake pumps of dopamine, norepinephrine, and serotonin, which phenethylamine and related molecules may as well to some extent, but with far less potency, such that it is basically insignificant in comparison. And, often being metabolized too quickly or not having the solubility to enable it to have a psychostimulant effect in humans. Claims that phenethylamine has comparable or roughly similar effects to psychostimulants such as amphetamine when administered are misconstrued. Phenethylamine does not have any obvious, easily discernible, reliably induced effects when administered to humans. Phenelzine’s enhancement of PEA levels may contribute further to its overall antidepressant effects to some degree. In addition, phenethylamine is a substrate for MAO-B, and treatment with MAOIs that inhibit MAO-B such as phenelzine have been shown to consistently and significantly elevate its concentrations.

Phenelzine usually requires six to eight weeks of treatment, and a minimum dose of 60 mg/day, to achieve therapeutic effects. The reason for the delay in therapeutic effect is not fully understood, but it is believed to be due to many factors, including achieving steady-state levels of MAO inhibition and the resulting adaptations in mean neurotransmitter levels, the possibility of necessary desensitisation of autoreceptors which normally inhibit the release of neurotransmitters like serotonin and dopamine, and also the upregulation of enzymes such as serotonin N-acetyltransferase. Typically, a therapeutic response to MAOIs is associated with an inhibition of at least 80-85% of monoamine oxidase activity.

Pharmacokinetics

Phenelzine is administered orally in the form of phenelzine sulfate and is rapidly absorbed from the gastrointestinal tract. Time to peak plasma concentration is 43 minutes and half-life is 11.6 hours. Unlike most other drugs, phenelzine irreversibly disables MAO, and as a result, it does not necessarily need to be present in the blood at all times for its effects to be sustained. Because of this, upon phenelzine treatment being ceased, its effects typically do not actually wear off until the body replenishes its enzyme stores, a process which can take as long as 2-3 weeks.

Phenelzine is metabolised primarily in the liver and its metabolites are excreted in the urine. Oxidation is the primary routine of metabolism, and the major metabolites are phenylacetic acid and parahydroxyphenylacetic acid, recovered as about 73% of the excreted dose of phenelzine in the urine over the course of 96 hours after single doses. Acetylation to N2-acetylphenelzine is a minor pathway. Phenelzine may also interact with cytochrome P450 enzymes, inactivating these enzymes through formation of a heme adduct. Two other minor metabolites of phenelzine, as mentioned above, include phenylethylidenehydrazine and phenethylamine.

Adverse Effects

Common side effects of phenelzine may include dizziness, blurry vision, dry mouth, headache, lethargy, sedation, somnolence, insomnia, anorexia, weight gain or loss, nausea and vomiting, diarrhoea, constipation, urinary retention, mydriasis, muscle tremors, hyperthermia, sweating, hypertension or hypotension, orthostatic hypotension, paraesthesia, hepatitis, and sexual dysfunction (consisting of loss of libido and anorgasmia). Rare side effects usually only seen in susceptible individuals may include hypomania or mania, psychosis and acute liver failure, the last of which is usually only seen in people with pre-existing liver damage, old age, long-term effects of alcohol consumption, or viral infection.

Interactions

The MAOIs have certain dietary restrictions and drug interactions. The amount of such restrictions and interactions is far less than previously thought, and MAOIs are generally safe medications when administered correctly. Hypertensive crisis is generally a rare occurrence while taking MAOIs, yet may result from the overconsumption of tyramine-containing foods. As a result, patients on phenelzine and other MAOIs must avoid excess quantities of certain foods that contain tyramine such as aged cheeses and cured meats, among others. Serotonin syndrome may result from an interaction with certain drugs which increase serotonin activity such as selective serotonin reuptake inhibitors, serotonin releasing agents, and serotonin agonists. Several deaths have been reported due to drug interaction-related serotonin syndrome such as the case of Libby Zion.

As is the case with other MAOIs, there is a concern regarding phenelzine and the use of both local and general anesthetics. Anyone taking phenelzine should inform their dentist before proceeding with dental surgery, and surgeon in any other contexts.

Phenelzine has also been linked to vitamin B6 deficiency. Transaminases such as GABA-transaminase have been shown to be dependent upon vitamin B6 and may be involved in a potentially related process, since the phenelzine metabolite phenylethylidenehydrazine (PEH) is a GABA transaminase inhibitor. Both phenelzine and vitamin B6 are rendered inactive upon these reactions occurring. For this reason, it may be recommended to supplement with vitamin B6 while taking phenelzine. The pyridoxine form of B6 is recommended for supplementation, since this form has been shown to reduce hydrazine toxicity from phenelzine and, in contrast, the pyridoxal form has been shown to increase the toxicity of hydrazines.

What is Tranylcypromine/Trifluoperazine?

Introduction

Tranylcypromine/trifluoperazine (brand names Parstelin, Parmodalin, Jatrosom N, Stelapar) is a combination formulation of the monoamine oxidase inhibitor antidepressant drug tranylcypromine and the typical antipsychotic drug trifluoperazine that has been used in the treatment of major depressive disorder.

It contains 10 mg tranylcypromine and 1 mg trifluoperazine.

The drug has been in clinical use since at least 1961. It is still available in Italy with the name of Parmodalin.

What is an Anxiolytic?

Introduction

An anxiolytic (also anti-panic or anti-anxiety agent) is a medication or other intervention that reduces anxiety.

This effect is in contrast to anxiogenic agents which increase anxiety. Anxiolytic medications are used for the treatment of anxiety disorder and its related psychological and physical symptoms.

Medications

Barbiturates

Barbiturates are powerful anxiolytics but the risk of abuse and addiction is high. Many experts consider these drugs obsolete for treating anxiety but valuable for the short-term treatment of severe insomnia, though only after benzodiazepines or non-benzodiazepines have failed.

Benzodiazepines

Benzodiazepines are prescribed to quell panic attacks. Benzodiazepines are also prescribed in tandem with an antidepressant for the latent period of efficacy associated with many ADs for anxiety disorder. There is risk of benzodiazepine withdrawal and rebound syndrome if BZDs are rapidly discontinued. Tolerance and dependence may occur. The risk of abuse in this class of medication is smaller than in that of barbiturates. Cognitive and behavioural adverse effects are possible.

Benzodiazepines include: Alprazolam (Xanax), Bromazepam, Chlordiazepoxide (Librium), Clonazepam (Klonopin), Diazepam (Valium), Lorazepam (Ativan), Oxazepam, Temazepam, and Triazolam.

Antidepressants

Antidepressant medications can reduce anxiety. The SSRIs paroxetine and lexapro and SNRIs venlafaxine and duloxetine are US Food and Drug Administration (FDA) approved to treat generalised anxiety disorder.

Selective Serotonin Reuptake Inhibitors

Selective serotonin reuptake inhibitors (SSRIs) are a class of medications used in the treatment of depression, anxiety disorders, OCD and some personality disorders. SSRIs can increase anxiety initially due to negative feedback through the serotonergic autoreceptors, for this reason a concurrent benzodiazepine can be used until the anxiolytic effect of the SSRI occurs.

Serotonin-Norepinephrine Reuptake Inhibitors

Serotonin-norepinephrine reuptake inhibitor (SNRIs) include venlafaxine and duloxetine drugs. Venlafaxine, in extended release form, and duloxetine, are indicated for the treatment of GAD. SNRIs are as effective as SSRIs in the treatment of anxiety disorders.

Tricyclic Antidepressants

Tricyclic antidepressants (TCAs) have anxiolytic effects; however, side effects are often more troubling or severe and overdose is dangerous. They’re effective, but they’ve generally been replaced by antidepressants that cause fewer adverse effects. Examples include imipramine, doxepin, amitriptyline, nortriptyline and desipramine.

Tetracyclic Antidepressant

Tetracyclic antidepressants, such as Mirtazapine, have demonstrated anxiolytic effect comparable to SSRIs while rarely causing or exacerbating anxiety. Mirtazapine’s anxiety reduction tends to occur significantly faster than SSRIs.

Monoamine Oxidase Inhibitors

Monoamine oxidase inhibitors (MAOIs) are first generation antidepressants effective for anxiety treatment but their dietary restrictions, adverse effect profile and availability of newer medications have limited their use. MAOIs include phenelzine, isocarboxazid and tranylcypromine. Pyrazidol is a reversible MAOI that lacks dietary restriction.

Sympatholytics

Sympatholytics are a group of anti-hypertensives which inhibit activity of the sympathetic nervous system. Beta blockers reduce anxiety by decreasing heart rate and preventing shaking. Beta blockers include propranolol, oxprenolol, and metoprolol. The Alpha-1 agonist prazosin could be effective for PTSD. The Alpha-2 agonists clonidine and guanfacine have demonstrated both anxiolytic and anxiogenic effects.

Miscellaneous

Buspirone

Buspirone (Buspar) is a 5-HT1A receptor agonist used to treated generalised anxiety disorder. If an individual has taken a benzodiazepine, buspirone will be less effective.

Pregabalin

Pregabalin (Lyrica) produces anxiolytic effect after one week of use comparable to lorazepam, alprazolam, and venlafaxine with more consistent psychic and somatic anxiety reduction. Unlike BZDs, it does not disrupt sleep architecture nor does it cause cognitive or psychomotor impairment.

Hydroxyzine

Hydroxyzine (Atarax) is an antihistamine originally approved for clinical use by the FDA in 1956. Hydroxyzine has a calming effect which helps ameliorate anxiety. Hydroxyzine efficacy is comparable to benzodiazepines in the treatment of generalised anxiety disorder. Hydroxyzine is typically only used for short term anxiety relief.

Phenibut

Phenibut (Anvifen, Fenibut, Noofen) is an anxiolytic used in Russia. Phenibut is a GABAB receptor agonist, as well as an antagonist at α2δ subunit-containing voltage-dependent calcium channels (VDCCs), similarly to gabapentinoids like gabapentin and pregabalin. The medication is not approved by the FDA for use in the United States, but is sold online as a supplement.

Mebicar

Mebicar is an anxiolytic produced in Latvia and used in Eastern Europe. Mebicar has an effect on the structure of limbic-reticular activity, particularly on the hypothalamus, as well as on all 4 basic neuromediator systems – γ aminobutyric acid (GABA), choline, serotonin and adrenergic activity. Mebicar decreases noradrenaline, increases serotonin, and exerts no effect on dopamine.

Fabomotizole

Fabomotizole (Afobazole) is an anxiolytic drug launched in Russia in the early 2000s. Its mechanism of action is poorly defined, with GABAergic, NGF and BDNF release promoting, MT1 receptor agonism, MT3 receptor antagonism, and sigma agonism thought to have some involvement.

Bromantane

Bromantane is a stimulant drug with anxiolytic properties developed in Russia during the late 1980s. Bromantane acts mainly by facilitating the biosynthesis of dopamine, through indirect genomic upregulation of relevant enzymes (tyrosine hydroxylase (TH) and aromatic L-amino acid decarboxylase (AAAD).

Emoxypine

Emoxypine is an antioxidant that is also a purported anxiolytic. Its chemical structure resembles that of pyridoxine, a form of vitamin B6.

Menthyl Isovalerate

Menthyl isovalerate is a flavouring food additive marketed as a sedative and anxiolytic drug in Russia under the name Validol.

Racetams

Some racetam based drugs such as aniracetam can have an antianxiety effect.

Etifoxine

Having similar anxiolytic effects as benzodiazepine drugs, etifoxine does not produce the same levels of sedation and ataxia. Further, etifoxine does not affect memory and vigilance, and does not induce rebound anxiety, drug dependence, or withdrawal symptoms.

Alcohol

Ethanol is sometimes used as an anxiolytic by self-medication. fMRI can measure the anxiolytic effects of alcohol in the human brain.

Alternatives to Medication

Cognitive behavioural therapy (CBT) is an effective treatment for panic disorder, social anxiety disorder, generalized anxiety disorder, and obsessive-compulsive disorder, while exposure therapy is the recommended treatment for anxiety related phobias. Healthcare providers can guide those with anxiety disorder by referring them to self-help resources. Sometimes medication is combined with psychotherapy but research has not found a benefit of combined pharmacotherapy and psychotherapy versus monotherapy.

If CBT is found ineffective, both the Canadian and American medical associations then suggest the use of a potent, long lasting benzodiazepine such as clonazepam and an antidepressant, usually Prozac for its effectiveness.