Pimozide: Mechanism of Action, Uses, and Side Effects

Antipsychotic drugs have been shown to be effective in reducing the most characteristic symptoms of schizophrenia, mainly hallucinations and delusions; however, this type of medication frequently causes extremely severe and difficult-to-tolerate adverse reactions that can even cause death.

In this article we will analyze the mechanism of action, uses and side effects of pimozide, one of the most potent antipsychotics available and also used to treat chronic and refractory tic disorders, especially of the Tourette syndrome.

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What is pimozide?

Pimozide is a psychoactive drug of the class of antipsychotics.. It belongs to the pharmacological group of diphenylbutylpiperidines, which also includes clopimozide, fluspirilene and penfluridol; all of them were developed by the Belgian company Janssen Pharmaceutica. Pimozide in particular was created in the year 1963.

It is a drug with a very intense potency, even more than that of other classic antipsychotics that are famous for their aggressiveness, such as haloperidol. This makes the risk of typical adverse reactions of antipsychotics, such as neuroleptic malignant syndrome and tardive dyskinesia, especially high when taking pimozide.

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What is your mecanism of action?

Pimozide exerts antagonistic effects on D2, D3 and D4 dopamine receptors, reducing the activity of this neurotransmitter in the central nervous system. This action is associated with a decrease in the positive symptoms of schizophrenia, the most characteristic of which are hallucinations and delusions.

Dopamine is the primary neurotransmitter in the brain's reward system, so reinforcement-motivated learning and behavior depend on this chemical. The symptoms of schizophrenia, both positive and negative, have been associated with dysfunctions in dopamine transmission.

The effects on dopamine are also the cause of the adverse reactions of the consumption of pimozide and other antipsychotics. Among these we find the extrapyramidal syndrome, which is characterized by the appearance of signs such as muscle stiffness and contractions, involuntary movements and physical and psychological restlessness.

What is pimozide used for?

Pimozide is mainly used for the treatment of two classes of psychological disorders of organic origin: psychoses and tics. In particular, this drug is administered in resistant and/or chronic cases of schizophrenia, Tourette syndrome and other alterations that fall into one of two of these categories.

Studies that have looked at the efficacy of pimozide compared to other more widely used antipsychotics drugs, such as chlorpromazine, show that they are about as effective in treating positive symptoms of the schizophrenia and other psychosis spectrum disorders.

Reference is also made in the scientific literature to the use of pimozide for disturbances related to paranoia and delusions; Thus, this drug is sometimes applied in the treatment of delusional disorder, in that of paranoid personality and in that of delusional disorder. delusion of parasitosis or Ekbom syndrome, typical of alcohol withdrawal syndrome.

Side effects and adverse reactions

The most common side effects of pimozide use include dizziness, drowsiness, excessive sweating (hyperhidrosis), dry mouth, constipation, repeated awakenings during the night due to the need to urination (nocturia), decreased muscle movements (hypokinesia or akinesia), and disturbances of speaks.

Other frequent and generally mild reactions that may appear are nervousness, feelings of weakness, postural changes, diarrhea, excessive salivation, increased thirst and hunger, sensitivity to light, abnormal movements, facial expressionlessness, and decreased performance sexual.

On the other hand, among Serious and characteristic side effects of antipsychotics we found neuroleptic malignant syndrome (which causes death in 10% of cases), tardive dyskinesia (movements repetitive and involuntary noises, often from the mouth) and akathisia (a feeling of intense discomfort and restlessness and constants).

There's also signs that the medication is acting in a negative way, so when they appear it is necessary to consult the doctor. The most important are confusion, fever, muscle stiffness, the appearance of neck contractures, difficulties swallowing and uncontrollable facial movements.

A particularly troublesome adverse reaction is the occurrence of heart rhythm disturbances. It is known that if the dose of pimozide is very high, this drug can cause sudden death because it favors the heartbeat to become irregular. Therefore, when pimozide is prescribed, electrocardiograms are usually scheduled.

Pimozide has also been found to cause tumor growth in mice. However, the available data do not allow this serious adverse reaction to be extrapolated to humans in a scientifically reliable manner.