Outcomes Associated with Generic Drugs Approved Using Product-Specific Determinations of Therapeutic Equivalence

We sought to examine rates of clinical outcomes among patients before and after market introduction of generic versions of five drugs approved using product-specific equivalence determinations. We used data from a large national insurer to identify patients who initiated a study (acarbose tablets, salmon calcitonin nasal spray, enoxaparin injection, vancomycin capsules, venlafaxine extended-release tablets) or control drug (nateglinide, glimepiride, alendronate, fondaparinux, metronidazole, sertraline, paroxetine) in each calendar month between 2003 and 2012 and to determine rates of claims-based proxies for lack of effectiveness outcomes following initiation. We used segmented time-series analyses to evaluate level (short-term) and slope (longer-term) changes in outcomes upon introduction of a generic study or control drug. Among study drugs, we observed three increases (one with p