Rispolettes Consta, 50 mg

Risperidone is a selective monoaminergic antagonist. It has high affinity for serotonergic 5-NT₂ receptors and dopaminergic D₂ receptors. In addition, risperidone binds to α₁-adrenergic receptors and, to a lesser extent, to H₁-histaminergic and α₂-adrenergic receptors. Risperidone does not bind to cholinergic receptors. Although risperidone is a potent D₂ receptor antagonist, which makes it improve the positive symptoms of schizophrenia, this drug, compared with typical neuroleptics, is less likely to depress motor activity and less likely to cause catalepsy. Because of its balanced central antagonism to serotonin and dopamine receptors, risperidone is less likely to cause extrapyramidal side effects and has a therapeutic effect on the negative and affective symptoms of schizophrenia.

Pharmacokinetics

Risperidone is metabolized by the CYP2D6 isoenzyme to 9-hydroxysperidone, which has the same pharmacological activity as risperidone itself. Risperidone and 9-hydroxysperidone form the active antipsychotic fraction. Another route of metabolism of risperidone is N-dealkylation.

In fast metabolizers, the clearance of the active antipsychotic fraction and risperidone is 5 and 13.7 L/h, respectively, and in weak metabolizers it is 3.2 and 3.3 L/h, respectively.

General characteristics of risperidone after injection in patients with Rispolept Consta^®

When Rispolett Consta^® is administered as a single injection in the body, the release profile of risperidone consists of a small initial phase (®.

The combination of the risperidone release profile and the dosing regimen (i.m. injection once every 2 weeks) ensures that therapeutic concentrations of risperidone are maintained in plasma. Therapeutic concentrations are maintained until the 4th to 6th week after the last injection of Rispolettes Consta®. The elimination phase is completed approximately 7-8 weeks after the last injection.

Risperidone is completely absorbed from Risolept Consta^® suspension. Risperidone is rapidly distributed in body tissues. V_d is 1-2 l/kg. In plasma, risperidone binds to albumin and α₁-acid glycoprotein. The plasma protein binding of risperidone is 90% and that of 9-hydroxyrisperidone is 77%. Following intravenous injections of Rispolept Consta^® at doses of 25 or 50 mg once every 2 weeks, mean plasma C_min and C_max values of the active antipsychotic fraction are 9.9-19.2 and 17.9-45.5 ng/mL, respectively. With this dosing regimen, the pharmacokinetics of risperidone are linear. No cumulation of risperidone was observed in long-term use (12 months) in patients who were administered Rispolept Consta^® once every 2 weeks at doses of 25-50 mg. A study of a single-dose oral form of risperidone showed higher plasma concentrations and decreased clearance of the active antipsychotic fraction by 30% in elderly patients and by 60% in patients with renal impairment. Plasma concentrations of risperidone in patients with hepatic impairment were normal, but the mean free plasma fraction was increased by 35%.

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