Pharmacovigilance (PV) is defined as the science and activities relating to the detection, assessment, understanding and prevention of adverse effects or any other drug-related problem.

Pharmacovigilance is needed to track unsuspected adverse drug reactions and events. Drug information collected during the pre marketing phase of all medical drugs is inevitable incomplete with regard to possible adverse reactions. Tests done in animals are insufficiently predictive of human safety.

In clinical trials patients are selected and limited in number and the conditions of use differ from those in clinical practice and the duration of trails is limited. The information about rare but serious adverse reaction, chronic toxicity, used in special groups such as children elderly and pregnant women or during drug interaction is incomplete or not available.