Journal of Bioequivalence & Bioavailability

Abstract

Current Issues on Bioavailability and Bioequivalence Determination

Chyung S. Cook

Methodologies for determining bioavailability and bioequivalence of endogenous compounds and macromolecules such as polymers are different from that of small exogenous compounds. In many cases, bioavailability and bioequivalence guidelines for exogenous molecules may not be appropriate for endogenous compounds. A common approach of baseline subtraction for endogenous materials is arguable in some cases, since levels of endogenous materials are highly variable during an experimental period. For polymers molecular weight distribution may be different among the materials from different manufactures and/or different manufacturing processes. These issues are addressed along with following issues regarding bioavailability/ bioequivalence determination: use of pharmacokinetic vs. pharmacodynamic parameters, use of a chiral assay vs. total assay for racemic drugs, and total vs. free concentration assays for drugs that exhibit concentration-dependent plasma protein binding, and for liposome/protein encapsulated formulations.