Little is known about the clinical consequences of different prescribing patterns between countries or between regions within a country. Systematic and comprehensive data are available on the use of drugs after they have been marketed, but it is recognized that such data are often not used to their full potential or in accordance with generally accepted criteria. Moreover, data on the effects of overdose and uncommon or long-term adverse effects are usually not available at the time of registration. To optimize the usefulness and/or benefits of drugs in actual use, continuing pharmacovigilance is needed. [1]

[1] For further information, contact the WHO Collaborating Centre for International Drug Monitoring, Stova tovget 3, S-753 Uppsala, Sweden. (Tel.: +46 (18) 656060; fax: +46 (18) 656080; e-mail: info@who-umc.org.)