Rispond Mechanism of Action

Antipsychotic agent.
Pharmacology: Risperidone is a benzisoxazole derivative.
Mechanism of Action: Risperidone's antipsychotic activity is attributed to its antagonistic activity at both dopamine (D₂ subtype) and serotonin (5HT₂ subtype) receptors. Risperidone is also an antagonist of α₁ and α₂ and H₁-receptor subtypes which mediate non-antipsychotic effects of risperidone.
Pharmacodynamics: Risperidone has been demonstrated to be efficacious in improving hallucinatory behaviour, paranoia, bizarre thought, content and conceptual disorganization when administered over a short term to patients of schizophrenia. During initiation of therapy, orthostatic hypotension can occur due to α-adrenergic receptor antagonism.
Pharmacokinetics: Absorption after oral administration is rapid and ranges up to 85% of the given dose. The absolute oral bioavailability of risperidone is approximately 70%. Plasma protein-binding is about 90%. Risperidone is extensively metabolized by the hepatic microsomal CYP-450 2D6 enzyme to 9-hydroxy-risperidone, an active metabolite. T_max=1-3 hrs. Half-life of elimination ranges from 3-20 hrs for the parent drug and 21-30 hrs for the metabolite.