• prescription-event monitoring;
  • adverse drug reactions;
  • general practice;
  • age;
  • gender;
  • post-marketing surveillance

Aims Little is known about the frequency with which suspected adverse drug reactions are seen by general practitioners after the prescription of newly marketed drugs. We investigated age and sex specific incidence rates of suspected adverse drug reactions recorded by general practitioners in England after the prescription of selected newly marketed drugs.

Methods Information was collected from 48 national cohort studies of newly marketed drugs studied by prescription-event monitoring. Questionnaires were sent to prescribers asking for details of events and suspected adverse drug reactions recorded in the patients’ notes occurring after the drugs were prescribed.

Results During the 48 cohort studies, a total of 513 608 patients were investigated, of which 221 781 (43.2%) were males and 285 862 (55.7%) were females. The overall incidence of suspected adverse drug reactions in males was 12.9 per 10 000 patient-months of exposure (95% confidence limits 12.3 to 13.5), and in females was 20.6 per 10 000 patient-months of exposure (95% confidence limits 19.9 to 21.3). The overall age-standardised relative risk of an adverse drug reaction in females compared with males was 1.6 (1.5–1.7). This sex difference was significant in all age groups above 19 years of age, and was relatively consistent across all age groups (χ2 test for heterogeneity=9.2, P=0.3).The highest rate of recording in males was in the 50–59 year age group, and in females was in the 30–39 year age group.

Conclusions In general practice in England, suspected adverse drug reactions to newly marketed drugs are recorded more often in adults aged between 30 and 59 years of age and are 60% more common in women than in men. The sex difference occurs in all age groups over 19 years of age.