Prochlorperazine (antipsychotic): uses, indications and side effects.

We analyze in which cases this psychotropic drug can be administered, and its effects.

Antipsychotic drugs](antipsychotic drugs) are mainly used to treat the psychotic symptomatology of some mental disorders, such as [schizophrenia]/clinical/schizophrenia). However, their indications go much further, and sometimes their chemical characteristics allow them to alleviate other types of symptoms.

This is the case with prochlorperazine, a classic antipsychotic drug, which also has antiemetic effects and antivertigo activity.. It is a type of piperazine phenothiazine, a group of antipsychotics. In this article we will learn about its characteristics, mechanism of action, uses, indications and side effects.

Prochlorperazine: characteristics

Prochlorperazine is a first-generation antipsychotic drug (also called a typical or classical antipsychotic), which can be used to treat schizophrenia (although, as we will see below, this is not its most frequent use).

Its mechanism of action is to antagonize the dopamine D₂ receptor.which leads to a decrease in the concentration of this substance. The trade name of Prochlorperazine is: Stemethyl.

On the other hand, dopamine is known to be found in elevated concentrations in people suffering from schizophrenia. That is why Prochlorperazine is a drug that can be used in this disorder, because it helps to decrease such dopamine concentrations.

Phenothiazines

At the chemical level, Prochlorperazine is derived from piperazinphenothiazine (or Piperazine Phenothiazines), a type of tricyclic neuroleptics (antipsychotics). Phenothiazines are a group of antipsychotics; specifically, the first to be used in the treatment of psychotic disorders, and the first to achieve positive results in alleviating their symptoms.

It can be said that the phenothiazines ushered in the era of psychopharmacology.. They are currently used to alleviate psychotic symptoms, but also to prevent nausea and vomiting (they are antiemetics), reduce hypertension (antihypertensives) and alleviate allergic symptoms (antihistamines). They are also used for other therapeutic purposes.

Piperazine phenothiazines

Piperazine phenothiazines, on the other hand, are a subtype of phenothiazines, from which Prochlorperazine is derived. In other words, Prochlorperazine is a phenothiazine with a piperazine structure. At the chemical and molecular level, piperazine phenothiazines have a piperazine or piperazinyl group in their side chain.

This subtype of phenothiazines, the piperazine phenothiazines, is the most potent of the phenothiazines. They have characteristics that allow them to be used for long-term treatment (chronic treatment) in patients with schizophrenia.

In terms of side effects, piperazine phenothiazines present extrapyramidal (movement-related) disorders. On the positive side, they are fast-acting drugs with little sedative action.

On the other hand, another advantage of Prochlorperazine, and piperazine phenothiazines in general, is that they do not cause orthostatic hypotension (or if they do, it is to a very small degree). Orthostatic hypotension involves a decrease in blood pressure; specifically, it is the inability of the body to regulate Blood Pressure rapidly.

Classical or typical antipsychotics

Antipsychotics, also called neuroleptics, can be of two types: classical (first generation or typical) and atypical (second generation). Those that were discovered first are the classical or typical ones. As we have seen, Prochlorperazine belongs to the first group.

The most important difference between these two groups of antipsychotics is that the atypical ones, besides acting on the positive symptoms of psychotic disorders (hallucinations, delusions, disorganized behavior...), have the advantage that they also act (although to a lesser extent) on the negative symptoms (abulia, affective flattening, apathy...). Another important difference is that atypicals do not cause extrapyramidal symptoms (symptoms caused by typical antipsychotics).

However, in terms of efficacy, both types of antipsychotics are equally effective. The important thing is to find the antipsychotic that best suits the patient's characteristics and pathology. and his or her pathology.

Mechanism of action

Thus, Prochlorperazine in particular, is a typical antipsychotic. Therefore, it presents the characteristics of this type of antipsychotic.

How does it act? By blocking the D₂ receptors of dopamine. This blockade affects four main brain pathways, where dopamine plays an essential role:

1. mesolimbic pathway blockade.

This is the most important blockade in relation to the therapeutic effects of Prochlorperazine (and of classical antipsychotics in general), since it involves the reduction of the positive symptoms of schizophrenia. That is, the therapeutic effect of the drug is produced by blocking the mesolimbic pathway of the brain.

2. Blockade of the nigrostriatal pathway

Thus, like all classical antipsychotics, Prochlorperazine also blocks the nigrostriatal pathway, which leads to movement disorders (the so-called Extrapyramidal Syndrome [EPS]). These alterations appear due to the decrease in dopamine produced by Prochlorperazine.

3. Blockade of the mesocortical pathway

The blockade of the third pathway, the mesocortical, does not produce any remarkable effect. On the other hand, when it comes to atypical antipsychotics, the blockade of this pathway improves the negative symptomatology of schizophrenia.

4. Blockade of the tuberoinfundibular pathway

Finally, the blockade produced by Prochlorperazine in the tuberoinfundibular pathway, another pathway with a large number of dopamine D₂ receptors, produces a series of effects: the most noteworthy is the increase in prolactin concentration, which causes gynecomastia (increase in breast size ["breasts grow" in both men and women]) and galactorrhea (increased milk production through the breasts). This is all due to decreased dopamine concentration.

Indications and other uses

Prochlorperazine, although indicated for the treatment of schizophrenia, is not as frequently used as an antipsychotic; however, is used especially as an antiemetic drug to reduce and alleviate nausea and vomiting (at lower doses than as an antipsychotic). (at lower doses than as an antipsychotic). On the other hand, Prochlorperazine is also frequently used to treat vertigo and so-called "severe labyrinthine disorders".

In addition, Prochlorperazine is used to treat headache and acute migraines (although this is neither an official nor an authorized indication; this concept is called "off label").

Finally, it appears that Prochlorperazine also has a "calming" effect and reduces painful symptoms; specifically, its effect has been found to be greater than that of hydromorphone (an analgesic drug derived from morphine) when applied intravenously, combined with diphenhydramine (a type of antihistamine).

Side effects

Prochlorperazine, like the other classical antipsychotics (with their respective nuances), has a number of side effects or adverse effectsOther symptoms may include constipation, headache (migraines), dry mouth, blurred vision, dizziness, feeling unsteady and/or difficulty maintaining balance, nausea and nasal congestion.

Other symptoms it may cause are: increased appetite (leading to weight gain), difficulty urinating, dilated or constricted pupils, agitation and/or nervousness, difficulty falling asleep or maintaining sleep (insomnia), drooling, uncontrollable tremors, gynecomastia and galactorrhea (already explained), among others.

These are just some of the symptoms that may appear when taking Prochlorperazine, but there are many others; moreover, they vary from one patient to another. The dose of Prochlorperazine taken, as well as its frequency of intake, can vary the manifestations of side effects.

Bibliographic references:

• Stahl, S.M. (2002). Essential psychopharmacology. Neuroscientific bases and clinical applications. Barcelona: Ariel.

• Malgor, L. and Valsecia, M. (2008). Psychopharmacology. Chapter 3: Neuroleptics, antipsychotics or major tranquilizers: 24-36. Medical Pharmacology.