Evaluating the bioavailability and bioequivalence of generic medications.

By law, the U.S. Food and Drug Administration (FDA) is permitted to approve generic versions of brand-name medications without necessarily requiring that research be conducted to prove them safe and effective, provided that a number of criteria are met. The most important criterion is bioequivalence. Bioavailability refers to the rate and extent to which the active ingredient is absorbed from a drug product. Maximum drug concentration (Cmax) is the parameter used to characterize the absorption rate. The area under the plasma drug concentration-time curve (AUC) is the parameter used to characterize the extent of drug absorption. Bioequivalence means that there is an equivalent rate and extent of absorption of the same active ingredient from two or more drug products. For a generic drug to be approved, both Cmax and AUC must vary only within a certain limited range compared with those for the brand name medication. Information about generic and pharmaceutical alternative drugs can be found in the Orange Book and via Drugs@FDA.