Objectives: To evaluate the research agenda of registered randomized trials comparing generic and branded drugs in terms of who sponsors them, whether they are published promptly, and whether they find favorable results. Methods: We included randomized trials that were registered in ClinicalTrials.gov or other registries from January 2000 to July 2015 comparing the safety or efficacy of brand name versus generic medications. To identify published manuscripts or results generated from such trials, we searched PubMed, Scopus, Google, and registry databases. Data were compared across sponsorship categories (“inbred” if the compared drugs were owned by the same company or its partners/subsidiaries, “competitive” if the compared drugs were owned by competing companies, and “apparently non-profit”), and time-to-publication was evaluated with Cox analysis. Results: We found 207 registered protocols reporting on 186 completed trials. Of those, 37 trials had been published and another 56 had posted results in registries, for a total of 93 trials with available results. Four years after completion, results were available for 46.4% of the trials, with substantial differences by sponsor: 70.8%, 28.1% and 46.2% of the inbred, competitive and non-profit trials. In multivariable modeling, inbred trials had 1.73-fold risk of having results available compared with competitive trials (P=.04). Almost all trials reported favorable results, with the exception of 4 (4.3% of the trials with results). Conclusion: Despite the importance of generics, relatively few randomized trials are registered comparing the health effects of generic versus branded medicines, with an unsatisfactory publication rate and almost ubiquitous favorable results. The overall literature on the topic is at high risk of bias, possibly in favor of generics. Higher non-profit funding and stronger pressure to register trials and publish results is needed.
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