ABSTRACT
As indicated in the previous chapter, when an innovative small-molecule drug product is going off patent, brand-name pharmaceutical and generic companies may file an abbreviated new drug application (ANDA) for approval of the generic copies of the innovative drug product. The innovative drug product is usually referred to as the brand-name drug product or reference product. A generic copy is a drug product identical to the reference drug which is the subject of an approved new drug application (NDA) with regard to active ingredient(s), route of administration, dosage form, strength, and conditions of use. Generic copies of the reference product are called test products. For the approval of generic drug products, the U.S. Food and Drug Administration (FDA) as well as other regulatory authorities require that evidence of bioequivalence in average bioavailability be provided through the conduct of pharmacokinetic (PK) bioequivalence studies. The assessment of bioequivalence in average bioavailability is usually referred to as the assessment of average bioequivalence (ABE). The assessment of bioequivalence as a surrogate endpoint for the evaluation of drug safety and efficacy is based on the Fundamental Bioequivalence Assumption that if two drug products are shown to be bioequivalent in average bioavailability, it is assumed that they are therapeutically equivalent. Note that, in clinical practice, many practitioners interpret that approved generic drug products can be used interchangeably since they are therapeutically equivalent to the brand-name drug.
