A watching brief

Monitoring of a drug’s safety continues even after it is prescribed to patients

Clinical trials can ensure a new drug is safe to use (or that its benefits outweigh its side-effects – no drug is completely safe). But even the biggest trials only include a few thousand patients for a limited period of time. When a drug is finally used in ‘real life’, rare side-effects may appear.

To capture these effects, most countries run a monitoring or pharmacovigilance system.

In the UK, the MHRA is responsible for monitoring new drug safety. This relies mainly on spontaneous reporting from doctors and other healthcare professionals via the yellow card system (which is named after the coloured slips that doctors complete to record side-effects). This system was introduced after the thalidomide episode. Although it’s useful, it has drawbacks – it’s likely to under-report adverse reactions, and it’s up to doctors to decide whether a reaction is linked to drug use.

Recently, the yellow card system has been expanded so patients can also report incidents via the internet.

In the 1980s, a complementary system – prescription event monitoring – was set up. This captures details of any adverse effect in the first 10,000 people given a drug, tracked through the prescription system.

In Europe, pharmacovigilance is coordinated by the European Medicines Agency, which draws information from national bodies and maintains a database of adverse drug reactions. This system can provide a warning about drugs that seem to be causing harmful reactions.

Lead image:

Michael Randall/Flickr CC BY NC

About this resource

This resource was first published in ‘Drug Development’ in January 2008 and reviewed and updated in August 2014.

Drug Development
Education levels:
16–19, Continuing professional development