Postmarketing surveillance.

Postmarketing drug surveillance refers to the monitoring of drugs once they reach the market after clinical trials. It evaluates drugs taken by individuals under a wide range of circumstances over an extended period of time. Such surveillance is much more likely to detect previously unrecognized positive or negative effects that may be associated with a drug. The majority of postmarketing surveillance concern adverse drug reactions (ADRs) monitoring and evaluation. Other important postmarketing surveillance components include unapproved or off-label drug use, problems with orphan drugs, and lack of paediatric formulations, as well as issues concerning international clinical trials in paediatric population. The process of evaluating and improving the safety of medicines used in paediatric practice is referred to as paediatric pharmacovigilance. It requires special attention. Childhood diseases and disorders may be qualitatively and quantitatively different from their adult equivalents. This may affect either benefit or risk of therapies (or both), with a resulting impact on the risk/benefit balance. In addition, chronic conditions may require chronic treatment and susceptibility to ADRs may change throughout the patient's lifetime according to age and stage of growth and development. Therefore, paediatric pharmacovigillance aspects need to be tailored to a number of variables based on heterogeneity of paediatric population. This chapter will summarize and discuss the key issues.