The risk of a newly diagnosed episode of upper gastrointestinal bleeding, acute liver and renal failure, agranulocytosis, aplastic anemia, severe skin disorders, and anaphylaxis was examined within 30 days after the first prescription for a low dose of diclofenac, naproxen, or ibuprofen in a cohort in the United Kingdom. We identified 22,146 persons using diclofenac (< or = 75 mg), 46,919 using naproxen (< or = 750 mg), and 54,830 using ibuprofen (< or = 1200 mg). Age, gender, and comorbidity were similar in the three cohorts. Overall 64 potential cases were identified, and 20 were confirmed by medical record review. Incidence rates (95% CI) of upper gastrointestinal bleeding/10,000 people using diclofenac, naproxen, and ibuprofen were 1.8 (0.5-4.6), 2.3 (1.2-4.2), and 0.4 (0.04-1.3), respectively. There were three cases of hepatic injury, one with naproxen and two with ibuprofen. Although low, the incidence of gastrointestinal toxicity remains the main serious adverse event for all study drugs
