Pharmacogenetics
Withdrawn medicines
17 The most common reason for medicines to be withdrawn from the market once they have been licensed is the subsequent occurrence in patients of serious adverse reactions, which were either unsuspected at the time of marketing authorisation or occur more frequently than was expected at the time of the grant of marketing authorisation.4 If at least some adverse reactions can be explained by genetic variation, pharmacogenetic analysis might enable medicines that have previously been licensed but then withdrawn to be reinstated, by allowing the prior identification of individuals likely to suffer from adverse reactions. It may also be the case that compounds already rejected during the process of development could be reconsidered as potential treatments for genetically-defined groups of patients.
18 However, there are various reasons why the re-licensing of withdrawn medicines will be difficult (paragraph 4.9). We conclude that medicines that are found to cause adverse reactions are unlikely to be re-licensed, even if pharmacogenetic analysis is subsequently carried out which could lead to the development of a useful test. An exception might arise in cases where there is no alternative treatment available. The low likelihood of pharmacogenetic analysis leading to the re-licensing of medicines is unfortunate, because there would be obvious benefits in reintroducing a medicine that is effective in one group of patients while eliminating the threat it poses to another group (paragraph 4.10).
Footnotes4 It is comparatively rare for medicines to be withdrawn from the market once they have been licensed. Between 1998 and 2002, the MCA awarded over 200 new licences, of which 12 were subsequently withdrawn because of safety concerns (National Audit Office (2003) Safety, quality, efficacy: regulating medicines in the UK (Norwich: The Stationery Office, HC 505)).