Клозапин

Yellow Crystalline Solid

Clozapine is a neuroleptic, which expresses antipsychotic and sedative action. It does not cause general depression and extrapyramidal disorders. It is used for severe and chronic forms of schizophrenia, maniacal conditions, manic-depressive psychosis, psychomotor excitement, and various other psychotic conditions.

ChEBI: A benzodiazepine that is 5H-dibenzo[b,e][1,4]diazepine substituted by a chloro group at position 8 and a 4-methylpiperazin-1-yl group at position 11. It is a second generation antipsychotic used in the treatment of psychiatr c disorders like schizophrenia.

Clozapine, a tricyclic neuroleptic, was introduced in 1972 for the treatment of psychosis. In 1975 its use was associated with cases of agranulocytosis, particularly in Finland. These cases, which included several fatalities, resulted in the withdrawal of the drug in some countries. However, clozapine remains available in at least 30 countries, in some cases only on special request, for the treatment of severe psychotic disorders unresponsive to other neuroleptics provided that close monitoring of the blood count is feasible. In 1989, it was introduced in the United States for the treatment of severe schizophrenia. Lately, the use of clozapine in the United Kingdom has been associated with convulsions. (Reference: (WHODIB) WHO Drug Information Bulletin, 2: 10, , 1977)

Clozapine, 8-chloro-11-(4-methyl-1-piperazinyl)5H-dibenzo[b,e] [1,4] diazepine (Clozaril), is a yellowcrystalline powder that is only slightly soluble in water. Withthe introduction of clozapine, a different pharmacological antipsychotics.106 Unlike typical antipsychotics, clozapine is largelydevoid of EPS. The lack of EPS with this compound waspostulated to be caused by its preferential binding tomesolimbic rather than striatal DA receptors.Furthermore,clozapine was shown to exhibit potent affinity for 5-HT2Areceptors.
DMCZ shows partial agonism at D₂ and D₃ receptors andexhibits a distinctly different pharmacological profile comparedwith clozapine and other atypical antipsychotics.Unlike clozapine, which is a potent M₁ muscarinic antagonist,DMCZ is a potent M₁ agonist. Agonism at muscarinicreceptors has been proposed to be useful for impaired cognitionin schizophrenia. Burnstein et al.found thatDMCZ acted as a partial agonist at DA D₂ and D₃ receptors.These investigators suggested that the low incidence of EPSassociated with clozapine may be caused by the partial agonismof DMCZ at D₂ and D₃ receptors. Thus, DMCZ maybe of interest as an atypical antipsychotic with an improvedside effect profile compared with clozapine.

Atypical antipsychotic drug, with a much lower tendency to cause extrapyramidal side effects than conventional neuroleptics. Displays a broad range of pharmacological actions; the antipsychotic effects are thought to be mediated principally by 5-HT 2A/2C and dopamine receptor blockade (K i values are 21, 170, 170, 230 and 330 nM for D 4 , D 3 , D 1 , D 2 and D 5 receptors respectively).

Although clozapine demonstrates a favorable pharmacologicalprofile compared with typical antipsychotics, its useis restricted by a relatively high incidence of agranulocytosis.The exact mechanism for the cause of agranulocytosishas not been confirmed, but a highly reactive nitrenium ionthat is formed by the action of hepatic enzymes appears tobe involved.The mean elimination half-life of clozapine following a single 75-mg dose is 8 hours. Because of severaladverse effects, clozapine is only used in refractory casesof schizophrenia. Individuals with a history of seizures orpredisposed to seizures should be cautioned when takingclozapine. Similar to other atypical antipsychotic agents,clozapine causes an increased risk of mortality in elderly individualswith dementia-related psychoses.

A serious drawback to the use of clozapine, however, is the potentially fatal agranulocytosis that is reported to occur in 1 to 2% of unmonitored patients, necessitating weekly white blood cell counts for at least the first 6 months of pharmacotherapy.

Clozapine is orally active and metabolized mainly by CYP3A4 to inactive desmethyl, hydroxyl, and N-oxide derivatives, with a half-life of approximately 12 hours. Clozapine has relatively low affinity for brain dopamine D1 and D2 receptors (moderate affinity for D4) in comparison to its affinity at adrenergic α1 and α2, histamine H1, muscarinic M1 and serotonin 5-HT2A receptors.