IMPORTANCE: Antithrombotic treatment is indicated for use in patients after myocardial infarction (MI); however, concomitant use of nonsteroidal anti-inflammatory drugs (NSAIDs) could pose safety concerns.

OBJECTIVE: To examine the risk of bleeding and cardiovascular events among patients with prior MI taking antithrombotic drugs and for whom NSAID therapy was then prescribed.

DESIGN, SETTING, AND PARTICIPANTS: Using nationwide administrative registries in Denmark (2002-2011), we studied patients 30 years or older admitted with first-time MI and alive 30 days after discharge. Subsequent treatment with aspirin, clopidogrel, or oral anticoagulants and their combinations, as well as ongoing concomitant NSAID use, was determined.

EXPOSURES: Use of NSAIDs with ongoing antithrombotic treatment after first-time MI.

MAIN OUTCOMES AND MEASURES: Risk of bleeding (requiring hospitalization) or a composite cardiovascular outcome (cardiovascular death, nonfatal recurrent MI, and stroke) according to ongoing NSAID and antithrombotic therapy, calculated using adjusted time-dependent Cox regression models.

RESULTS: We included 61,971 patients (mean age, 67.7 [SD, 13.6] years; 63% men); of these, 34% filled at least 1 NSAID prescription. The number of deaths during a median follow-up of 3.5 years was 18,105 (29.2%). A total of 5288 bleeding events (8.5%) and 18,568 cardiovascular events (30.0%) occurred. The crude incidence rates of bleeding (events per 100 person-years) were 4.2 (95% CI, 3.8-4.6) with concomitant NSAID treatment and 2.2 (95% CI, 2.1-2.3) without NSAID treatment, whereas the rates of cardiovascular events were 11.2 (95% CI, 10.5-11.9) and 8.3 (95% CI, 8.2-8.4). The multivariate-adjusted Cox regression analysis found increased risk of bleeding with NSAID treatment compared with no NSAID treatment (hazard ratio, 2.02 [95% CI, 1.81-2.26]), and the cardiovascular risk was also increased (hazard ratio, 1.40 [95% CI, 1.30-1.49]). An increased risk of bleeding and cardiovascular events was evident with concomitant use of NSAIDs, regardless of antithrombotic treatment, types of NSAIDs, or duration of use.

CONCLUSIONS AND RELEVANCE: Among patients receiving antithrombotic therapy after MI, the use of NSAIDs was associated with increased risk of bleeding and excess thrombotic events, even after short-term treatment. More research is needed to confirm these findings; however, physicians should exercise appropriate caution when prescribing NSAIDs for patients who have recently experienced MI.