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Center for Health Services and Outcomes Research

Health Policy

Effect of Therapeutic Class on Generic Drug Substitutions

The use of generic drugs in place of branded drug products results in lower prices to insurers and patients. The U.S. Food and Drug Administration (FDA) assures that an approved generic product provides the same quality, safety, and efficacy as the corresponding brand. Despite this, some clinicians and patients are reluctant to use generic medications. Sometimes, this is based on a concern that even a small difference in absorption or metabolism impacts outcomes [such as drugs with very narrow therapeutic indices (NTI)]. In other cases, however, the reasons for “generic reluctance” are ambiguous. If the societal goal is to allow patients to access worthy medications while containing costs within the health care system, we need to understand why there is differential acceptance of generic drugs.

As requested by the FDA, we have entered into a cooperative agreement to advance knowledge about usage of generic drugs, substitution of generic drugs for brand-name drugs, and the modifiers of generic drug use at the patient, prescriber, and health system level. We hypothesized that the factors which influence generic drug use vary by therapeutic class. We will: 1) quantify generic drug usage in the U.S. by therapeutic classes and assess predictors of generic substitution; 2) quantify patient-reported concerns about generic drugs, by therapeutic class, and to identify risk factors for patient-reported concerns in response to generic substitution; and 3) develop an evaluation scheme to prioritize drugs requiring generic product development and investment and to apply the evaluation scheme to identify priority drugs.