The import-substituted drug product driven pharmaceutical industry in the developing countries as well as the generic drug industry should have a clear understanding of the critical considerations in pharmaceutical bioequivalence testing. In particular, the factors influencing bioavailability/ bioequivalence measurements, formulation design, development and evaluation, along with study design for assessment bioavailability and bioequivalence are pivotal to the development of a good generic product. Additionally, the intricacies associated with bioequivalence assessment of highly variable drugs, food effects in bioequivalence evaluations and the relevance of pharmacodynamics in bioequivalence studies need to be appreciated while developing a new generic product. In so doing, the resultant equivalent product will be dependable and predictable in terms of its activity, both drug release and therapeutic, thus addressing some of the contemporary issues that revolve around pharmaceutical bioequivalence.

The intention of this presentation, in addition to reviewing the fundamentals of bioequivalence, is to present a consolidated and comprehensive look at those intricacies germane to design, development and evaluation of pharmaceutical bioequivalent product. In particular,the following sections will be addressed: a) definition and difficulties in acceptance criteria, b)bioequivalence assessment of highly variable drugs with special emphasis on significance of reference product and single versus multiple dose studies, and c)superbioavailability. Keywords : Bioavailability, Bioequivalence, Highly variable drugs, Superbioavailability