The rationale for a post-marketing surveillance.

Post-marketing surveillance is essential in order to protect patients against avoidable risks from medication. Complete assessment of a drug cannot, for practical reasons, be made before marketing. There are several methods which can be used in post-marketing surveillance. Spontaneous reporting on adverse drug reactions is a quick method, but underreporting is a problem. Intensive monitoring gives high quality data but is expensive. Health registers can be used to trace cases for case-control studies but diagnoses are sometimes incorrect. Prospective studies is an informative way to obtain results but they take time. Data on drug utilization are also valuable because they give an estimate of the size of the population using a particular drug. They also reveal whether warnings about adverse drug reactions have had any effect on the prescribing pattern.