Is it possible to achieve bio-equivalence between an oral solid immediate-release and an analogue enteric-coated formulation?

While bioequivalence between enteric-coated and immediate-release formulations can be achieved in terms of AUC, gastric emptying of enteric-coated dosage forms is a stochastic event, usually leading to lower Cmax values than those observed with the corresponding immediate release. This article examines challenges of developing enteric-coated dosage forms which are bioequivalent to the corresponding immediate-release formulations in terms of both AUC and Cmax using rasagiline as a model compound. In vitro drug release profiles of enteric-coated formulations were obtained and compared to those of the immediate-release formulation by dissolution testing. Pharmacokinetics was evaluated in bioequivalence studies in healthy human volunteers after single oral administration of enteric-coated and immediate-release formulations. The initial enteric-coated pellet formulation prototype was equivalent in terms of AUC, but differed in Cmax ; a second formulation prototype, consisting of a single-unit core and enteric-coating film, proved to be bioequivalent to immediate-release rasagiline tablets in terms of AUC and Cmax . In vitro, it released rasagiline rapidly at a pH of 6.8. Despite differences in gastric emptying between disintegrating immediate-release and enteric-coated solid dosage forms, bioequivalence in pharmacokinetic studies was achieved.