In Vivo Bioequivalence and In Vitro Similarity Factor (f2) for Dissolution Profile Comparisons of Extended Release Formulations: How and When Do They Match?

ABSTRACTPurposeTo investigate how likely two extended release formulations are to be bioequivalent when they demonstrate f2 similarity.MethodDissolution profiles were simulated using the Weibull model and varying model parameters around those of a reference profile. The f2 values were calculated for the comparisons of each simulation with the reference profile. The in vivo inputs obtained from an in vitro-in vivo correlation model were convolved with a unit impulse response function. The AUC, Cmax, and Tmax from each simulated in vivo concentration profile were compared to the reference profile. The AUCR (AUC ratio) and CmaxR (Cmax ratio) were determined. The consistency between f2 and bioequivalence was investigated.ResultsThe relationships between AUCR, CmaxR, f2 and the Weibull model parameters demonstrate that the bioequivalence regions enclosed by the contour lines of 80% and 125% of AUCR and CmaxR were generally close to the regions enclosed by the f2 = 50 contour line, but did not exactly match, especially when Dmax and B deviated from the reference values.ConclusionsWhen f2 is used for in vitro dissolution profile comparison, the completeness of the dissolution profiles should not differ more than 10%, and the shapes of the dissolution profiles should not be significantly different.