The rates of common adverse events reported during treatment with proton pump inhibitors used in general practice in England: cohort studies

Aims To estimate the rates of common adverse events in patients treated wit h the proton pump inhibitors omeprazole, lansoprazole and pantoprazole in g eneral practice in England. Methods In prescription-event monitoring cohort studies, data on dispensed prescriptions prescribed by general practitioners in England soon after eac h drug was launched were linked to subsequent clinical events recorded by t he prescriber. 16 205 patients prescribed omeprazole between June 1989 and June 1990, 17 329 patients prescribed lansoprazole between May and November 1994, and 11 541 patients prescribed pantoprazole between December 1996 an d June 1997 were studied. Results The commonest adverse events in the omeprazole, lansoprazole and pa ntoprazole cohorts were diarrhoea (incidence: 0.18, 0.39 and 0.23 per 1000 days of exposure, respectively); nausea/vomiting (incidence: 0.16, 0.22 and 0.18 per 1000 days of exposure, respectively); abdominal pain (incidence: 0.17, 0.21 and 0.17 per 1000 days of exposure, respectively); and headache (incidence rates: 0.10, 0.17 and 0.15 per 1000 days of exposure, respective ly). The remaining adverse events occurred at rates of less than 0.11 per 1 000 days of exposure. There were little absolute differences in the rates o f most events between the three proton pump inhibitors. However, diarrhoea was more commonly associated with lansoprazole compared with omeprazole (ra te difference: 0.21 per 1000 days of exposure; 95% CI 0.17, 0.25; rate rati o: 2.11; 1.78, 2.51), and there was a clear age-response relationship. Conclusions Adverse events occurred relatively infrequently in all three co horts. There were only small absolute differences in event rates between th e three drugs, although these data suggest the hypothesis that lansoprazole is associated with more frequent occurrence of diarrhoea, particularly in the elderly.