Summary

Prescription-event monitoring (PEM) is a method of independent pharmacovigilance conducted at the Drug Safety Research Unit (DSRU) in Southampton.  Exposure data are systematically obtained for patients dispensed a monitored drug in the immediate post-marketing period.  Questionnaires are subsequently sent to patients general practitioners (GPs) asking them to report each patient's clinical happenings (events) during treatment with a PEM drug.  Doctors are not asked to give an opinion about the cause of these events.  The rationale for monitoring "events" rather than "suspected drug reactions" is well established and event monitoring allows the detection of unsuspected drug reactions.  PEM studies are intended to augment the United Kingdom (UK) spontaneous reporting scheme.  In PEM studies both the number of patients in the cohort and the duration of treatment for these patients are known which enables incidence rates for reported events to be calculated.  So not only is the nature of the reported events determined but also the frequency of each event is calculated in a way that can be compared with those for other PEM drugs within the same therapeutic class.