Reone Mechanism of Action

Pharmacology: Pharmacodynamics: Risperidone is a monoaminergic antagonist with high affinity (Ki of 0.12 to 7.3 nM) for the serotonin Type 2 (5HT2), dopamine Type 2 (D2), α1 and α2 adrenergic, and H1 histaminergic receptors. Risperidone showed low to moderate affinity (Ki of 47 to 253 nM) for the serotonin 5HT1C, 5HT1D, and 5HT1A receptors, weak affinity (Ki of 620 to 800 nM) for the dopamine D1 and haloperidol-sensitive sigma site, and no affinity (when tested at concentrations >10-5 M) for cholinergic muscarinic or β1 andβ2 adrenergic receptors.
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 meditated by the cytochrome P450 isoenzyme CYP2D6 and is the subject of generic polymorphism. Excretion is mainly in the urine and, to a lesser extent, in the faeces. Risperidone and 9-hydroxyrisperidone are about 90% and 77% bound to plasma proteins, respectively. Both are distributed into breast milk.