Risperidone: effects of formulations on oral bioavailability.

The bioavailability of risperidone was evaluated in an open-label, randomized, two-way, crossover study comparing a 1-mg tablet with a 1-mg/ml oral solution. Both formulations were administered as a single 1-mg dose with a 10-day washout period between treatments. Of 26 healthy men who entered the study, 23 completed both treatment periods. Plasma concentrations of risperidone and the active moiety (risperidone plus its active metabolite, 9-hydroxyrisperidone) were determined by radioimmunoassays. For key pharmacokinetic values (Cmax, AUC), the 90% CIs on the relative bioequivalence of risperidone, 9-hydroxyrisperidone, and the active moiety were contained within the equivalence range of 80-120% (80-125% for log-transformed data). The results demonstrate that the 1-mg/ml oral solution and the 1-mg tablet are bioequivalent.