Modified prescription-event monitoring studies: a tool for pharmacovigilance and risk management.

Prescription-Event Monitoring (PEM) is a well established postmarketing surveillance technique designed to monitor the overall safety of newly marketed medicines as used in real-life clinical practice, usually in cohorts of at least 10 000 patients. At the Drug Safety Research Unit in the UK we are now moving towards a more targeted safety surveillance known as Modified PEM (M-PEM). These studies combine the advantages of conventional PEM studies (in monitoring general safety and identification of unexpected risks of a medicine) with that of a more targeted safety study that addresses specific questions (to better understand known or partially known risks with a medicine). Through the use of enhanced data collection questionnaires, M-PEM expands the range of applications of conventional PEM, which include more detailed characterization of real-life drug use, adherence to prescribing recommendations and targeted analysis of events requiring special monitoring by regulatory authorities. A particularly useful application is the evaluation of the safety of a medicine in special populations or subgroups (e.g. patients switching from another therapy or patients with a particular risk factor) or following important changes in the product's lifecycle (e.g. a licensing or formulation change). M-PEM studies therefore have an important contribution to make to pharmacovigilance and the risk management of medicines by providing valuable information on the use of new medications under real-life situations.