The Impact of Generic Substitution on Health and Economic Outcomes: A Systematic Review

BACKGROUND Generic drugs are considered therapeutically equivalent to their original counterparts and lower in acquisition costs. However, the overall impact of generic substitution (GS) on global clinical and economic outcomes has not been conclusively evaluated. OBJECTIVE To test whether (1) generics and original products yield the same health outcomes, and (2) generic therapies save economic resources versus original therapies. METHODS We performed a systematic literature review in Medline, Embase, and the Cochrane Database of Systematic Reviews to identify original studies that examine clinical or economic outcomes of GS. After standardized data extraction, reported outcomes were categorized as supporting or rejecting the hypotheses. Each reported outcome was assessed and accounted for supporting and opposing GS. One publication could provide multiple outcome comparisons. RESULTS We included 40 studies across ten therapeutic areas. Fourteen studies examined patients on de novo therapy; 24 studies investigated maintenance drug therapy, and two studies considered both settings. Overall, 119 outcome comparisons were examined. Of 97 clinical outcome comparisons, 67% reported no significant difference between generic drugs and their off-patent counterparts. Of 22 economic comparisons, 64% suggested that GS increased costs. Consequently, hypothesis (1) was supported but hypothesis (2) was not. We found no major differences among studies that investigated clinical outcomes with de novo or maintenance therapy. CONCLUSION The review suggests that clinical effects are similar after GS. However, economic savings are not guaranteed. More systematic research comparing clinical and economic outcomes with or without GS is needed to inform policy on the use of generic substitution.