Antipsychotics

**counselor** Mon Oct 15, 2012 10:51 am

Antipsychotics [drugs]

The drugs. comprise a series of compounds belonging to different chemical classes, but which induce, in animals and humans, effects at the biochemical, pharmacological and behavioral partly overlapping. The neurotransmitter system most affected by these drugs appears to be that dopamine (dopamine), but, especially in the last generation drugs (atypical antipsychotics), is of fundamental importance the action on the serotonergic system (serotonin). The drugs. in this sense can be divided into first generation antipsychotics or neuroleptics, characterized by a predominant and differentiated blocking action on ubiquitous dopaminergic receptors of type D2, and atypical antipsychotics, the action of which is characterized by an action blocker more marked on serotonergic receptors 5-HT2 than dopamine receptor, demonstrating, on the latter, topomimetica action on dopamine receptors type D3 and D4, more localized in limbic areas. In turn, the neuroleptics can be divided into various classes, represented by phenothiazines, butyrophenones, difenilbutilpiperidine, thioxanthenes, substituted benzamides, dibenzoxazepine. Some neuroleptics (eg., The butyrophenones) show a high power level to block dopamine D2 receptors and others (eg., Some phenothiazines) are instead part of neuroleptics block dopamine at low power. From such a high pharmacological potency depends on both the incisiveness antipsychotic action, especially on positive symptoms of schizophrenia, for the reduction of the dopaminergic tone limbic, is, unfortunately, the appearance of extrapyramidal effects and hormonal (especially the increase in prolactin), respectively due to the block level in dopaminergic nigrostriatal and tuber-infundibular level. Among the neuroleptics rather low power (eg., Chlorpromazine, thioridazine etc.) Causes less extrapyramidal side effects, but prevail, as a result of the action of blocking receptors on phenothiazines a-adrenergic, muscarinic and histaminergic, the effects of type autonomic (hypotension, sedation, weight gain, central and peripheral anticholinergic action): among them, of considerable clinical advantage is the sedative action of some compounds, useful in some psychotic patients during the acute phase. The neuroleptic drugs show therefore a good deed on the positive symptoms of schizophrenia, but insufficient level on negative symptoms, as well as the risk of inducing extrapyramidal disorder, acute and chronic. Almost equivalent action on positive symptoms, negative symptoms, but more action and less extrapyramidal Collateral, is demonstrated by atypical antipsychotics for their action mainly on 5-HT2 receptors and on specific subsystems and dopamine receptors. They are divided into two main classes: the SDA (a. a predominantly dopaminergic and serotonergic) and MARTA (a. action multiple receptor). Among the SDA are better known as risperidone, sertindole and the ziprasidone: these drugs are characterized not only by the action of block serotonin greater dopaminergic that, from a-adrenergic receptor blockade, which involves some cautions relating to blood pressure and cardiovascular Collateral in general. Among the MARTA are used clozapine, the prototype for these atypical, olanzapine, quetiapine and zotepine the: that class, interacting with many subtypes (adrenergic, histaminergic, muscarinic etc.), Side effects prevalent type of autonomic. Both the SDA and the MARTA to the pharmacological characteristics referred to above, present, especially at low to medium doses, low extrapyramidal Collateral, acute and late, and with some drugs, even minor Collateral hyperprolactinaemic.