Clinical relevance of the bioavailability/bioequivalence controversy.

A generic drug containing the same active ingredient as a brand name drug may not show identical clinical efficacy. There is increasing evidence that substitution of a generic for a brand name (or vice versa) drug with the expectation of similar results is problematic and that improper treatment may result. Clinical trials are needed to test generic psychoactive drugs. This paper provides guidelines for clinical situations in which problems relating to bioavailability and bioequivalence may arise, for example, in patients taking concomitant medication(s) or in chronically ill or elderly patients. In addition, the importance of knowing which assay methods are used to measure psychoactive drug blood levels in considering drug efficacy is stressed.