Clinical trials on drug-drug interactions registered in ClinicalTrials.gov reported incongruent safety data in...

To assess safety data of trials on drug-drug interactions (DDIs) reported in ClinicalTrials.gov and published in journal articles, since DDIs are a growing concern.

In an observational study of clinical trials retrieved by the search term "drug-drug interaction(s)," we collected the information on registration and on adverse events (AEs) from ClinicalTrials.gov and corresponding publications. Trials were included if they primarily investigated DDIs, had a National Clinical Trial identifier, and were closed and completed by October 16, 2015. Publication data were extracted until March 2017.

Among 1,110 eligible trials, most were in phase 1 (76.8%), industry-funded (68.8%), and started before registration (56.9%). Results were not reported in the registry for 86.8% and not published for 68.1% trials. Published AE data were completely identical to the data submitted to ClinicalTrials.gov for only 15.6% trials. Among 64 trials with results reported both in ClinicalTrials.gov and publications, 34.4% published concordant number for other AEs.

Discrepancies that emerge from incomplete or changed reporting of AEs in publications emphasize the need to amend and enforce regulatory requirements for timely and complete submission of results, clearer AE reporting for trials focusing on DDIs, and regular assessment of the congruence of AE data submitted to ClinicalTrials.gov and scientific journals during the publication process.