Is reporting rate a good predictor of risks associated with drugs?

Aims Uncertainty as to relative under-reporting plagues the comparisons of spontaneous reporting rates as a tool for decision-making in pharmacovigila nce. However, it is generally accepted that under-reporting should be reaso nably similar for similar drugs sharing the same indication, country and pe riod of marketing. To test this, we compared the adverse drug reaction repo rting rates to the French regional pharmacovigilance centres for six pairs of identical drug marketed at the same time by different companies under di fferent brand names (co-marketing). Methods All reaction reports were related to sales, to compute reporting ra te; within each pair, the reporting rate ratio and its confidence interval were calculated. Results The rate ratios were all between 0.76 and 1.33. Two of them were si gnificantly different from 1 (1.28; 95% C.I. [1.01; 1.60] and 1.33; 95% C.I . [1.06; 1.74]). Conclusions These small differences in reporting rates would not warrant re gulatory action and support the usual assumption of similar reporting for s imilar drugs.