Prescription-event monitoring : Frequently asked questions

What is prescription-event monitoring?

Prescription-event monitoring or PEM is a method of studying the safety of new medicines that are used by general practitioners (GPs). It is a national scheme covering the whole of England. Using this method, the Drug Safety Research Unit based in Southampton, has completed more than 90 PEM studies since 1980.

What is the Drug Safety Research Unit (DSRU)?

The Drug Safety Research Unit is an independent registered charity (No. 327206) associated with the University of Portsmouth whose work is principally concerned with pharmacovigilance, the detection of side-effects associated with drugs.

Why is PEM necessary?

Studies in animals and clinical trials conducted before a medicine becomes generally available are very useful, but have important limitations. Some side-effects can only be detected when a medicine is taken by large numbers of patients in ordinary, day-to-day usage. It is vital that safety is continuously monitored and this is particularly important when a medicine is new. PEM complements other monitoring methods (such as the Yellow Card scheme for reporting suspected adverse drug reactions which is run by the government).

How does PEM work ?

Patients prescribed a study medicine are identified from dispensed prescriptions sent by pharmacists to a processing centre (the Prescription Pricing Division or PPD, formally PPA – part of the National Health Service Business Services Authority – NHSBSA) for payment purposes. After an interval of at least 6 months, a questionnaire is sent by the Drug Safety Research Unit to the GP who prescribed the medicine for that particular patient. This requests information on all medical events that have occurred since the study drug was prescribed. A medical event is defined as any new illness, change in an existing illness or reason for medical consultation (e.g. in relation to pregnancy), regardless of whether it not it was thought to be related to treatment. The information received is then analysed and used to monitor the safety of the new medicine.

What is the difference between a medical event and a side-effect?

A medical event may or may not be related to treatment, whereas a side-effect is a suspected or established consequence of taking a particular medicine (or combination of medicines). For example, a bone fracture is an event which could simply be due to trauma (and therefore unrelated to medical treatment) or it could be a side-effect of a medicine which tended to make bones thinner. PEM collects information about all events and tries to use the information to determine which events might be side-effects.

Who pays for PEM?

The Drug Safety Research Unit has several sources of income. It receives unconditional charitable donations from the pharmaceutical industry. This means that the industry does not commission or have any control over individual PEM studies. Other sources of income include revenue generated from running training courses in pharmacovigilance and research grants from a variety of sources.

What ethical issues are involved?

Because patients are studied after a medicine has been prescribed, PEM is an “observational” method which does not intervene in patient care. It is recognised in national ethical guidelines as a method of inquiry which is in the public interest.

What about the confidentiality of information?

All prescription information received from the PPD and the anonymised medical information received from GPs is treated in strict confidence by the DSRU, which is allowed under the Data Protection Act of 1998 to hold such information for research purposes.