Lack of bioequivalence between generic risperidone oral solution and originator risperidone tablets

Risperidone is an atypical anti-psychotic, available in various formulations. OBJECTIVE: The objective of the study was to compare the bioavailability of a generic oral solution of risperidone (Test formulation) and Risperdal tablets (Reference formulation). Both formulations contained 1 mg risperidone per dosing unit. METHODS: The study was carried out in 32 healthy volunteers under fasting conditions. Risperidone and 9-hydroxyrisperidone concentrations in plasma were determined using HPLC/MS/MS. RESULTS: The results show that the 90% confidence intervals for the geometric mean ratios of the solution and the tablet formulations were not within the acceptance range of 80 125% for risperidone, whereas the confidence intervals for 9-hydroxyrisperidone were within the acceptance range of 80 - 125%. CONCLUSION: Bioequivalence between the generic 1 mg/ml risperidone solution and the originator tablet formulation was not proven in this study.