Risponz/Risponz 1/Risponz 2/Risponz 3 Mechanism of Action

Antipsychotic.
Pharmacology: Pharmacodynamics: Risponz 1/Risponz 2/Risponz 3: Risperidone (Risponz) is an antipsychotic of the benzisoxazole derivatives. It is a selective monoaminergic antagonist. Risperidone (Risponz) has affinity for serotonin‑5‑HT2, dopamine‑D2, H1‑histaminic, alpha 1 and alpha 2‑adrenergic receptors. Risperidone (Risponz) has no affinity for cholinergic receptors. It is a potent D2‑antagonist.
Pharmacokinetics: Risponz 1/Risponz 2/Risponz 3: Risperidone (Risponz) is completely absorbed after oral administration. Peak plasma concentrations are attained within 1 to 2 hours. Food does not affect the absorption of Risperidone.
Risperidone is metabolized by cytochrome P‑450 11D6 to 9‑hydroxy‑Risperidone which has a similar pharmacological activity to Risperidone. Risperidone and 9‑hydroxy‑risperidone form the active antipsychotic fraction.
After oral administration to psychotic patients, Risperidone's half‑life is about 3 hours. The elimination half‑life of 9‑hydroxy‑risperidone and the active antipsychotic fraction is 24 hours.
Following 6 mg or 8 mg once daily, peak levels of the active moiety were about 30% higher and trough levels about 30% lower than the peaks and troughs following 3 and 4 mg twice daily.
Steady state is reached within 1 day for Risperidone (Risponz) in most patients and 4‑5 days for 9‑hydroxyrisperidone. Risperidone plasma concentration is dose-proportional within the therapeutic dose‑range. Risperidone (Risponz) is bound to albumin and alpha1‑acid glycoprotein. Plasma protein binding of Risperidone is 88% and 77% for 9‑hydroxy‑risperidone. One week after administration, 70% of the dose is excreted in the urine and 14% in the faeces. In urine, Risperidone and 9‑hydroxy‑risperidone represent 35‑45% of the dose. Risperidone (Risponz) showed higher active plasma concentrations and slower elimination in the elderly and in patients with renal insufficiency. The plasma concentrations of Risperidone (Risponz) were normal in patients with liver insufficiency.
The pharmacokinetics of Risperidone, 9‑hydroxy‑risperidone and the active moiety in children are similar to those in adults.
Risponz: Risperidone is readily absorbed after oral doses, peak plasma concentrations being reached within 1 to 2 hours. It is extensively metabolised 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 faeces. Risperidone and 9-hydroxyrisperidone are about 90% and 77% bound to plasma proteins, respectively.