Pharmacokinetics and tolerability of long-acting risperidone in schizophrenia

The pharmacokinetics and tolerability of long-acting risperidone (Risperdal Consta™) were evaluated in a multicenter, prospective, open-label, 15-week study of 86 patients with schizophrenia. Subjects stabilized on 2, 4 or 6 mg of oral risperidone once daily for at least 4 weeks were assigned to receive i.m. injections of 25, 50 or 75 mg of risperidone, respectively, every 2 weeks for 10 weeks. The 90% confidence intervals for the i.m./oral ratios of the mean steady-state plasma-AUC, corrected for dosing interval, and of the average plasma concentration of the active moiety (risperidone plus 9-hydroxyrisperidone) were within the range of 80–125%, indicating bioequivalence of the i.m. and oral formulations. However, mean steady-state peak concentrations of the active moiety were 25–32% lower with i.m. than oral dosing ( P