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 intense and difficult to tolerate adverse reactions that can lead to death.

In this article we will analyze the mechanism of action, uses and side effects of pimozide one of the most powerful antipsychotics that exist and is also used to treat chronic and treatment-resistant tic disorders, especially Tourette syndrome.

What is pimozide?

Pimozide is a psychotropic drug in the antipsychotic class 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 1963.

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

What is your mecanism of action?

Pimozide exerts antagonistic effects on dopamine D2, D3 and D4 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 main neurotransmitter in the brain’s reward system, so learning and behavior motivated by obtaining reinforcement depend on this chemical compound. 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 adverse reactions from the use of pimozide and other antipsychotics. Among these we find extrapyramidal syndrome, which is characterized by the appearance of signs such as muscle rigidity 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 these categories.

Studies that have looked at the effectiveness of pimozide compared to other more commonly used antipsychotics, such as chlorpromazine, find that they are approximately equally effective in treating the positive symptoms of schizophrenia and other psychosis spectrum disorders.

In the scientific literature, reference is also made to the use of pimozide for alterations related to paranoia and delusions; Thus, this drug is sometimes applied in the treatment of delusional disorder, paranoid personality disorder, and parasitic delirium or Ekbom syndrome, typical of alcohol withdrawal syndrome.

Side effects and adverse reactions

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

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

On the other hand, among the Serious and characteristic side effects of antipsychotics We find neuroleptic malignant syndrome (which causes death in 10% of cases), tardive dyskinesia (repetitive and involuntary movements, frequently of the mouth) and akathisia (a feeling of intense and constant discomfort and restlessness).

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

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

It has also been found that pimozide can cause tumors to develop in mice. However, the available data do not allow this serious adverse reaction to be extrapolated to humans in a scientifically reliable manner.