Scope and purposes of pharmacovigilance

In the past, the process of pharmacovigilance has often been considered to start when a drug is authorised for use in ordinary practice. Nowadays, it is more commonly considered to include all safety-related activity beyond the point at which humans are first exposed to a new medicinal drug. 

The ultimate purpose of pharmacovigilance is to minimise, in practice, the potential for harm that is associated with all active medicines. Although data about all types of ADRs are collected, the main focus is on identifying and preventing those which are defined to be serious. This means an ADR which meets at least one of the following criteria  

Additionally, all congenital abnormahties are considered serious and the definition of serious allows the appUcation of medical judgement such that a reaction may be considered serious, even if there is not clear evidence that one of the above criteria is met. 

In order to minimise harms there is first a need to identify and assess the impact of unexpected potential hazards. For most medicines, serious ADRs are rare otherwise their detection would result in the drug not reaching or being withdrawn from the market. For products which do reach the market, serious hazards are seldom identified during pre-marketing clinical trials because sample sizes are almost invariably too small to detect them. In addition, the prevailing conditions of clinical trials - selected patients, short durations of treatment, close monitoring and specialist supervision - almost invariably mean that they will underestimate the frequency of ADRs relative to what will really occur in ordinary practice. 

During pre-marketing clinical development, the aims of pharmacovigilance are rather different to the broad public health function described above. In volunteer studies and clinical trials there 

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