WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT: Non-steroidal anti-inflammatory drugs (NSAIDs) and paracetamol are widely used analgesics in the prescription and non-prescription settings. Although both classes of drug are generally well tolerated, they can lead to well-characterized adverse effects. Both drugs are widely co-prescribed and it is of interest to understand better safety outcomes when the two drugs are taken concomitantly. WHAT THIS STUDY ADDS?: Relative rates and hazard ratio patterns of safety outcomes were broadly similar for patients prescribed ibuprofen alone, paracetamol alone and concomitant ibuprofen and paracetamol. The risks of the various safety outcomes examined do not appear to be modified by concomitant use of ibuprofen and paracetamol compared with paracetamol or ibuprofen alone. AIMS: To evaluate and compare the risk of specific safety outcomes in patients prescribed ibuprofen and paracetamol concomitantly with those in patients prescribed ibuprofen or paracetamol alone. The outcomes were evaluated according to dose, duration and exposure. METHODS: The study used a retrospective longitudinal cohort design with data from the UK General Practice Research Database (GPRD). The study population included patients aged 18 years or over who were prescribed ibuprofen alone, paracetamol alone or concomitant ibuprofen and paracetamol (tablets or capsules only). The safety outcomes evaluated were upper gastrointestinal events, myocardial infarction, stroke, renal failure (excluding chronic), congestive heart failure, intentional or accidental overdose, suicidal behaviour and mortality. Time-dependent Cox regression was used to estimate relative rates for the safety outcomes, by treatment group. A further analysis evaluated whether the hazard rates (i.e. absolute risks) varied over time with changes in drug exposure. RESULTS: The study population included 1.2 million patients. There was considerable heterogeneity in both patient and exposure characteristics. When comparing with past users, for most safety outcomes, current users of concomitant paracetamol and ibuprofen had relative rates between those for current users of ibuprofen alone and paracetamol alone. The hazard rates were generally proportional over time, from current to past exposure, following a prescription for concomitant paracetamol and ibuprofen compared with ibuprofen alone or paracetamol alone. CONCLUSIONS: The known risk of the safety outcomes examined does not appear to be modified by concomitant use of ibuprofen and paracetamol compared with paracetamol or ibuprofen alone.