Status of generic substitution: problematic drug classes reviewed.

The Drug Price Competition and Patent Term Restoration Act of 1984 enticed numerous manufacturers to enter the generic drug market. Even though products marketed under this act must be bioequivalent to brand name products and must meet the same FDA standards for quality, reports of inequivalence have appeared in the literature. However, cases of inequivalence and lack of efficacy have also been reported with brand name drugs. Discussed in this article are current data on the use of brand name versus generic products of several problematic drugs and drug classes--thyroid preparations, conjugated estrogens, digoxin, phenothiazines, theophylline, and anticonvulsants. Also included in this article is an explanation of the terms used in discussions of brand name and generic drugs, a review of recent changes in legislation that pertain to the development of brand name and generic drugs, and recommendations of steps to take (in-house and federal) when problems with medications are discovered.