Spontaneous adverse drug reaction reporting vs event monitoring: a comparison.

Spontaneous adverse drug reaction (ADR) reporting is the mainstay of national and international drug safety evaluation in the post-approval phase. A major criticism of the method has been a high, but essentially unquantifiable, level of under-reporting by doctors. A direct comparison has been made between spontaneous ADR reporting and an observational event monitoring system for a group of more than 44,000 patients receiving one or other of a group of seven new drugs. The data suggests that under-reporting by the spontaneous system may be as high as 98% for several clinical events believed to be associated with drug treatment.