Prescriber profile and post-marketing surveillance.

The response rate to requests to general practitioners (GPs) to supply post-marketing data on new drugs has been falling within the prescription-event monitoring (PEM) system organised by the Drug Safety Research Unit in Southampton, UK. To find out why, we looked at the characteristics of prescribers and the pattern of their prescribing for twenty seven PEM drugs and 543,788 treatments dispensed in England between September, 1984, and June, 1991. 28,402 GPs identified during PEM studies were divided into six groups according to the largest number of prescriptions for one or more of the drugs, ranging from group 1 (none of the drugs prescribed) to group 6 (one or more drugs for over 60 patients). From group 1 to group 6 the proportion of the GPs who were women decreased from 46% to 9%, and the proportion of overseas-qualified doctors increased from 13% to 47%. 10% of doctors who had prescribed most heavily accounted for 42% of total prescribing. 19 doctors had each prescribed a drug for more than 120 patients during the early post-marketing period. There was a consistent inverse relation between the number of prescriptions and the response to requests for post-marketing information. The overall response was 53% but the heaviest 10% of prescribers returned only 44% and the heaviest 1% returned only 34% of questionnaires. No differences in medical need can account for such variations in prescribing practice. Heavy prescribing by a minority of doctors during the period immediately following licensing for marketing may be placing patients at unnecessary risk. These doctors also affect the success of attempts to monitor the safety of new drugs.