Haloperidol, chlorpromazine, clozapine, risperidone, olanzapine, ziprasidone or quetiapine are the names of some of the best known and most widely used antipsychotics or neuroleptics . These are substances that help keep the symptoms of various mental disorders under control, especially schizophrenia and other psychotic disorders.

In this article we will talk about the last one mentioned, quetiapine , to see what kind of substance it is, in which cases it is used and its possible side effects.

Quetiapine: what it is and mechanisms of action

As indicated in the introduction, quetiapine is a drug with psychoactive effects that falls under the category of atypical antipsychotics . It is a dibenzothiazepine-type substance, being structurally closely related to olanzapine and especially to clozapine.

Its mechanism of action is based on its effects on dopaminergic and serotoninergic receptors , acting by blocking the D2 dopamine receptors in the brain and those of serotonin (which it also reduces, which causes that at a general level the level of dopamine in most cortical structures is maintained as this inhibits dopamine).

This is a great advantage, since it is common in schizophrenia to have an excess of dopamine at the mesolimbic level and a deficit of it in the mesocortical pathway, generating positive symptoms (hallucinations, delusions, aggressiveness, impulsiveness and disorganization) and negative symptoms (alogia and abulia, among others), respectively. If we only try to reduce dopamine, as typical antipsychotics do in a non-specific way in the area to be treated, we would not be working and could even worsen the existence of the negative ones, besides generating alterations in other areas with normative levels.

In addition to its effect on dopamine and serotonin, also has histaminergic and cholinergic effects , affecting and reducing the levels of both. This last factor causes some drowsiness and weight gain, as well as hypotension and some physiological and memory alterations

Quetiapine has a big advantage over other antipsychotics, and that is that it usually does not generate any kind of motor side effects. This is why subjects with psychotic problems who also suffer from Parkinson’s can take it (as long as there is no dementia), and it is usually given as a drug to replace treatment with clozapine or olanzapine when they give extrapyramidal side effects. There are usually no sexual effects either, and prolactin levels are not altered. This indicates that its action at the nigrostriatal and tuberoinfundibular level is minimal, generally not causing effects on the dopamine levels of these pathways.

Main indications and uses

Quetiapine is a psychodrug that is very useful for a large number of people and is used in clinical practice for various disorders and problems. The most common ones are the following.

1. Schizophrenia

The main and best known indication of quetiapine is schizophrenia . In this sense, quetiapine shows a great effect at the level of treatment of both positive symptoms (understanding as such those that add characteristics and/or generate an increase in activation, such as hallucinations and delusions) and negative ones (the opposite, as occurs in poverty of thought and/or speech).

2. Other psychotic disorders

Although schizophrenia is the primary target of most antipsychotics, it is not the only psychotic-type disorder that exists. People with disorders such as brief psychotic disorder, schizophrenia, schizoaffective disorder, and chronic delusional disorder may also benefit from the action of quetiapine.

3. Bipolar disorder

Some second generation antipsychotics, including quetiapine, have been used in the treatment of manic episodes in subjects with bipolar disorder . And not only in the treatment of crises, but also sometimes prophylactically to prevent them from happening. Furthermore, it also reduces the symptomatology of depressive episodes that occur in this same disorder.

4. Major depressive disorder

Since 2010, quetiapine has been approved for the treatment of major depressive disorder in some countries. Although it is not the most recommended treatment, it is an alternative that has proven to be effective in those cases of depressed subjects for whom conventional antidepressants do not work.

Side effects and contraindications

As with other drugs, quetiapine use can lead to a number of undesirable side effects . For this reason, among other things, its use must always be indicated and supervised by specialised doctors.

The most common side effect and common to all antipsychotics is the possible sedation or drowsiness of the subject, together with weight gain . Hypotension and possibly tachycardia are also common, so special caution should be taken in patients with heart problems. Hyperglycemia is also common, and can sometimes contribute to the development of diabetes (special care should be taken and a doctor should be consulted if there is extreme thirst or hunger, an exaggerated increase in the desire to urinate or weakness, fruity breath or a metallic taste as this could be a symptom of a potentially life-threatening ketoacidosis due to excess blood sugar).

Problems such as constipation, dry mouth and blurred vision , along with dizziness and hyperthermia, are also relatively common. Due to its anticholinergic action it can also generate memory disorders. Although it occurs in very few cases, it can lead to jaundice, endocrine problems and epileptic seizures. Asthenia, nervousness, akathisia, dryness and liver disorders may also occur.

In severe cases, fever, bleeding, falls, convulsions, priapism , tachycardia or breathing difficulties may occur. Also allergies and inflammation of the liver. Finally, the possibility of neuroleptic malignant syndrome should be taken into account (which is why the doctor regulates the dose to a great extent and tends to increase it very gradually until it reaches the desired levels).

Contraindications

Regarding contraindications, quetiapine is contraindicated in all patients suffering from heart problems or vulnerability to them. It is also contraindicated in diabetic subjects, due to weight gain and glycemic level as well as the metabolic alterations it can produce.

Quetiapine should also not be taken by those who require the use of other drugs (especially cytochrome P450 3A4 inhibitors present in some HIV or erythromycin medications, for example), and they should consult their doctor.

Finally, should be taken with great caution by pregnant and lactating women . You should not drive or operate heavy machinery under its effects, especially because of the sedation it can cause.

Bibliographic references:

  • Navarro, B.; Montejo, A. & Martín, M. (2003). Utility of quetiapine in tardive dyskinesia. Actas Esp. Psiquiatr; 31 (6): 347-352.
  • Rodríguez, J.; Fernández, R.; Iglesias, J. Carnero, M.A.; Quintero, P. & Pascual, F. (n.d.). Quetiapina. Pharmacotherapy Information Bulletin. 3 (5). Xerencia de Atención Primaria de Ourense.
  • Salazar, M.; Peralta, C.; Pastor, J. (2011). Manual of Psychopharmacology. Madrid, Editorial Médica Panamericana.
  • Srisurapanont, M.; Disayavanish, C. & Taimkaew, K. (2001). Quetiapine for schizophrenia (Cochrane Review). In: The Cochrane Library, 2.

    • .