Psychosis refers to symptoms such as delusions, hallucinations, disorganised thinking and speech, and bizarre and inappropriate motor behaviour that indicate loss of contact with reality.
A number of mental disorders cause symptoms of psychosis (Schizophrenia and Related Disorders).
Anti-psychotic drugs can be effective in reducing or eliminating symptoms of psychosis.
They appear to be most effective in treating hallucinations, delusions, disorganised thinking, and aggression.
Although anti-psychotic drugs are most commonly prescribed for schizophrenia, they appear to be effective in treating these symptoms whether they result from schizophrenia, mania, dementia, or use of a substance such as amphetamines.
After the immediate symptoms have cleared, depending on the cause of their psychosis, individuals may need to continue taking anti-psychotic drugs to reduce the probability of future episodes.
How Do Anti-Psychotic Drugs Work?
Anti-psychotic drugs work by influencing how information is transmitted between individual brain cells.
The adult brain is made up of more than 10 billion nerve cells called neurons. Each neuron in the brain has a single long fiber called an axon, which transmits information to other neurons. Like wires connected in a vast telephone switchboard, each neuron makes contact with several thousand other neurons.
Information travels down a cell’s axon as an electrical impulse. When the impulse reaches the end of the axon, a tiny amount of a chemical called a neurotransmitter is released to pass information on to the next cell down the line. A receptor on the receiving cell detects the neurotransmitter, which causes the receiving cell to generate a new impulse.
Symptoms of psychosis appear to be caused by excessive activity of cells sensitive to the neurotransmitter dopamine. Therefore, anti-psychotic drugs work by blocking receptors so that communication between groups of cells is reduced.
How well different anti-psychotic drugs block different types of neurotransmitters varies.
Every effective anti-psychotic drug known blocks dopamine receptors.
The newer anti-psychotic drugs (asenapine, clozapine, iloperidone, lurasidone, olanzapine, quetiapine, risperidone, and ziprasidone) also block receptors for serotonin, another neurotransmitter.
Experts thought that this property might make these drugs more effective. However, recent studies have not supported this view.
Clozapine, which also blocks many other receptors, is clearly the most effective drug for psychotic symptoms. But it is not commonly used because of its serious side effects and the need for monitoring with blood tests.
What are the Types of Anti-Psychotic Drugs?
Anti-psychotic drugs are divided into two groups:
- First-generation (conventional, older) anti-psychotics
- Second-generation (newer) anti-psychotics.
Currently, about 95% of anti-psychotics prescribed in the United States are second-generation anti-psychotics. Medical professionals have thought that second-generation anti-psychotics were somewhat more effective, but recent evidence casts doubt on this. They may have lower likelihood of some of the more serious adverse effects of first-generation drugs.
Second-generation anti-psychotic drugs may relieve positive symptoms (such as hallucinations), negative symptoms (such as lack of emotion), and cognitive impairment (such as reduced mental functioning and attention span). However, medical professionals are not sure whether they relieve symptoms to a greater extent than the older anti-psychotic drugs or whether individuals are just more likely to take them because they have fewer side effects.
Clozapine, the first of the second-generation anti-psychotic drugs, is effective in up to half of people who do not respond to other anti-psychotic drugs.
However, clozapine can have serious side effects, such as seizures or potentially fatal suppression of bone marrow activity (which includes making blood cells). Thus, it is usually used only for individuals who have not responded to other anti-psychotic drugs. People who take clozapine must have their white blood cell count measured weekly, at least for the first six (6) months, so that clozapine can be stopped at the first indication that the number of white blood cells is decreasing.
Some conventional and second-generation anti-psychotics are available as long-acting injectable preparations that need to be given only once every month or two. These preparations are useful for many individuals, including those who cannot reliably take oral drugs every day.
What are the Side-Effects of Anti-Psychotic Drugs?
Anti-psychotic drugs have significant side effects, which can include:
- Drowsiness;
- Muscle stiffness;
- Tremors;
- Weight gain; and
- Restlessness.
Some newer second-generation anti-psychotic drugs have fewer side effects.
The risk of tardive dyskinesia, muscle stiffness, and tremors is significantly lower with these drugs than with the conventional anti-psychotics.
However, some of these drugs seem to cause significant weight gain. Some also increase the risk of metabolic syndrome. In this syndrome, fat accumulates in the abdomen, blood levels of triglycerides (a fat) are elevated, levels of high-density cholesterol (HDL, the “good” cholesterol) are low, and blood pressure is high. Also, insulin is less effective (called insulin resistance), increasing the risk of type 2 diabetes.
- Tardive Dyskinesia:
- This s a hyperactive involuntary movement disorder that can be caused by anti-psychotic drugs.
- It is more likely with first-generation than second-generation drugs.
- Tardive dyskinesia is characterised by puckering of the lips and tongue or writhing of the arms or legs.
- Tardive dyskinesia may not go away even after the drug is stopped.
- For tardive dyskinesia that persists, there is no effective treatment, although the drugs clozapine or quetiapine may relieve symptoms a little.
- However, the new drug valbenazine has been found to be effective in improving symptoms of tardive dyskinesia.
- Individuals who must take anti-psychotic drugs for a long time are checked every 6 months for symptoms of tardive dyskinesia.
- Neuroleptic Malignant:
- This syndrome is a rare but potentially fatal side effect of anti-psychotic drugs.
- It is characterised by muscle rigidity, fever, high blood pressure, and changes in mental function (such as confusion and lethargy).
- Long-QT Syndrome:
- This is a potentially fatal heart rhythm disorder that can be caused by several anti-psychotics in both classes.
- These drugs include:
- Thioridazine;
- Haloperidol;
- Olanzapine;
- Risperidone; and
- Ziprasidone.
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