Are There Any Differences Between Generics and Brand-Name Drugs?
However, it should be noted that current regulations permit a variation of approximately 20% either way in the bioavailability of the active ingredient. (The specifics of the permitted variation in bioavailability hinge on the FDA’s technical definition of bioequivalence, which requires that there be no statistically significant difference in bioavailability. For the FDA’s definition, see the agency’s Guidance for Industry document, which sets out guidance on confidence intervals for test to reference comparisons across different types of medications, as well as the FDA’s Code of Federal Regulations 320 document on bioavailability and bioequivalence requirements. Also see this 1999 Food and Drug Law Institute overview of the Hatch-Waxman Act of 1984.) In one study (Borgheini 2003), a full 31% variation was found in the blood plasma levels of a particular medication after a patient switched from a branded to a generic product. (Why does this happen? It may be accounted for by difference
