Types of antipsychotics (or neuroleptics)

April 6, 2024

There is a great diversity of theories and hypotheses about psychotic disorders , its causes and the way to treat them. These disorders are a great detriment to those who suffer, and produce a strong anguish for both the person and those around her. They interfere in cognitive abilities, social relationships and in the emotional sphere, altering contact with reality. Being disorders that limit the normative functioning of the human being, its treatment is essential .

Based on the research carried out, from a side of the psychotropic drugs have been developed several substances and active ingredients that can help to treat this type of problems. It is about the different types of antipsychotics or neuroleptics .

Psychotic disorders

For most people, the word schizophrenia is not unknown. It refers to one of the main and most well-known psychotic disorders, a group of disorders characterized by the presence of perceptions, ideas and behaviors far from the normative, normally with some loss of contact with reality .

This type of disorders usually involve two types of symptoms: positive ones, which provoke or add something to the habitual behavior, perception or flow of thought, and negative ones as those symptoms that flatten and produce a deficit in the psychosocioemotional state of the sufferer.

The most typical and well-known examples of the symptoms of psychotic disorders are the presence of abnormal perceptions or hallucinations and that of more or less structured belief systems, the so-called delusions. Although the negative symptoms are less visible, they stand out the loss of logic and coherence in thinking, poverty in language and poverty of thought or praise.

Let us now focus on one of the forms of treatment, pharmacological, reviewing the different substances that are used in the presence of psychotic symptoms.

Mechanism of action of neuroleptics

The drugs dedicated to combat the symptoms of psychotic disorders are called antipsychotics or neuroleptics. Formerly known as major tranquilizers , this type of drug combats with great success the typical symptoms, especially the positive ones.

This type of psychoactive drug focuses mainly on the neurotransmitter known as dopamine, due to the high level of relationship found between this hormone and psychotic symptoms .

Specifically, it has been considered that an excess of dopamine in the mesolimbic pathway causes the presence of positive symptoms such as hallucinations and delusions , while a dopaminergic deficit at the mesocortical level is the most likely cause of negative symptoms like poverty of thought and praise. That is why the mechanism of action of drugs that address these problems will focus on working with dopamine at the level of synthesis, reuptake and transmission. However, among the different types of antipsychotics there are differences and nuances in the way they work, as we will see.

In addition to the treatment of psychotic disorders, some neuroleptics have been used for other types of problems, such as some motor, affective or personality disorders (for example, in the case of borderline disorder).

Types of antipsychotics

Traditionally, antipsychotics or neuroleptics have been classified into two large groups, the classic or typical neuroleptics and the atypical ones.

1. Classic or typical antipsychotics

Discovered by chance in the fifties, typical antipsychotics are those with which the pharmacological treatment of psychotic disorders was initiated . This type of drugs exert their action by blocking the dopamine D2 receptors of the mesolimbic pathway, reducing the excess of this hormone in the system and causing the cessation of positive symptoms.

Within this group of antipsychotics we found some as well known as haloperidol, chlorpromazine or levomepromazine , along with others such as pimozide, zuclopenthixol or fluphenazine. They can be administered both directly and in depot presentation, in which the substance is injected into the muscle in a crystallized form so that it is released slowly over time (in cases where there is little willingness to take medication or little control of the monitoring of the treatment).

However, despite its great utility, the typical neuroleptics are nonspecific, so that the blockade of dopaminergic receptors does not occur only in the mesolimbic pathway. This causes other pathways that also depend on dopamine to be altered , also affecting the mesocortical pathway, from which apparently appears the negative symptoms due to a deficit of dopamine. Because classical neuroleptics act by blocking their uptake, the typical antipsychotics they have virtually no effect on the negative symptoms, and may even make them worse .

Adverse effects

In addition to this, other pathways such as the nigrostriatal and the tuberoinfundibular, which in psychotic disorders need not be altered in their own way, also inhibit dopamine uptake. Adverse effects may occur in the form of movement disorders such as akathisia, parkinsonian syndrome and dyskinesia , or of sexual alterations such as amenorrhea or gynecomastia. These symptoms are not only annoying, but it can cause neuroleptic malignant syndrome, which could lead to death. Therefore it is necessary to carefully guide the consumption of these drugs, following the prescriptions of the professionals and being able to change the antipsychotic in order to reduce discomfort and adverse effects.

It is for this reason that the subsequent investigation focused on investigating and develop other antipsychotics that have a positive effect on negative symptoms and do not produce as many side effects . This does not mean that the typical antipsychotics have stopped being used, since they are very effective and the adverse symptoms can be controlled with another medication (antiparkinsonian for the case of motor problems, for example).

2. Atypical antipsychotics

Considering the little effect of conventional antipsychotics on the negative symptoms and the high number of unwanted side effects that they entail, subsequent research has tried to create new substances that overcome the deficiencies of this type of neuroleptic, creating safer and more effective drugs. effective These safer drugs have been labeled as atypical antipsychotics or neuroleptics .

Within the atypical antipsychotics we find substances of different families and compositions, so depending on which is used will have a greater or lesser effect on various problems. The main drugs that fall into this category are clozapine, olanzapine, risperidone, sulpiride, quetiapine and ziprasidone .

Differences with respect to classical neuroleptics

As with conventional, atypical antipsychotics they work by blocking dopamine D2 receptors , which in the mesolimbic pathway would have an inhibitory effect of this neurotransmitter, which causes the cessation of positive symptoms. But nevertheless, In addition to this the atypical antipsychotics have an effect on serotonin , also producing an antagonistic effect with respect to this.

It is necessary to take into account that serotonin acts as an inhibitor of dopamine release. Therefore, the effect that atypical antipsychotics cause on the tuberoinfundibular and nigrostriatal pathways (which would be affected by a conventional neuroleptic) generates an interaction between dopamine and serotonin that would leave the level of dopamine equal to or close to what would be normal. In other words, The presence of possible adverse effects is greatly reduced .

However, given that in the cerebral cortex there are more serotonin than dopamine receptors, the fact of inhibiting serotonin causes an increase in the release of dopamine, which stops its release. That is to say that although part of its functioning blocks the release of dopamine, the fact that it inhibits an inhibitor of its release that is much more present and extended makes the total level of dopamine higher. For this reason, Atypical antipsychotics do have an effect on negative symptoms by increasing the crude dopamine level in the mesocortical way.

With all this, the atypical neuroleptics they represent an advance that produces improvement in both positive and negative symptoms and they generate a smaller number of adverse effects (although they have some).

Risks and side effects of taking antipsychotics

We have commented briefly that taking antipsychotics can cause different undesirable side effects, some especially dangerous . These effects can be controlled with the taking of other medications or by changing the neuroleptic, having to evaluate the possible effects and the appearance of adverse effects after its administration. Some of the main risks and side effects of the different types of antipsychotics are the following.

1. Motor symptoms

One of the pathways affected secondarily by the taking of antipsychotics is nigrostriatal, which is linked to motor control.

In this way, Extrapyramidal syndrome is common , in which there are symptoms such as parkinsonian tremors, the appearance of involuntary movements in tardive dyskinesia, the disappearance of spontaneous movements of akinesia or the motor restlessness of akathisia.These symptoms occur mainly when taking conventional or typical antipsychotics, and their occurrence is not frequent with atypical antipsychotics.

2. Sexual symptoms

The taking of certain neuroleptics can cause different sexual symptoms, usually due to the involvement of the tuberoinfundibular way (especially in the pituitary gland). Within this type of symptoms highlights the cessation of menstrual flow or amenorrhea, as well as galactorrhea or emission of milk through the breasts regardless of sex and gynecomastia or breast growth, also regardless of the sex of the patient. Although in general only occur with typical antipsychotics, there are some cases with certain atypical, such as risperidone .

3. Sedation

As we have seen, one of the original names of antipsychotics is that of major tranquillizers. This term was not given by chance , and is that the taking of antipsychotics produces a sedation effect that can be more or less powerful.

4. Neuroleptic malignant syndrome

This syndrome is one of the most serious side effects that can cause the taking of antipsychotics, being able to take the patient to coma or even to death. It is characterized because the individual suffers from tachycardia, arrhythmias, high fever, muscular rigidity and loss of consciousness. to. However, it is a very infrequent syndrome.

5. Agranulocytosis

Described in the case of clozapine, this possible side effect is somewhat serious in causing the levels of red and white blood cells to get out of control. It can be lethal, so it is necessary to have blood tests as a control method.