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Pharmacology: Pharmacodynamics: Risperidone is a benzisoxazole derivative with antipsychotic property. It selectively antagonizes serotonin effects via cortical 5-HT2 receptor, and to a lesser extent, competes with dopamine at the limbic dopamine D2 receptor. This leads to decreased psychotic effects.
Pharmacokinetics: Risperidone is readily absorbed after oral doses, peak plasma concentrations being reached within 1 to 2 hours. It is extensively metabolized in the liver by hydroxylation to its main active metabolite, 9-hydroxyrisperidone; oxidative N-dealkylation is a minor metabolic pathway. Hydroxylation is mediated by the cytochrome P450 isoenzyme CYP2D6 and is the subject of genetic polymorphism.
Excretion is mainly in the urine and to a lesser extent, in the feces. Risperidone and 9-hydroxyrisperidone are about 88% and 77% bound to plasma protein, respectively.
