Allopurinol use and risk of non-fatal acute myocardial infarction

Objectives To quantify the risk of non-fatal acute myocardial infarction (AMI) among users of allopurinol. Methods We carried out a population-based case–control study over the period 2001–2007 in patients aged 40–90 years. Patients who had prescriptions of allopurinol or an episode of AMI before the start date of follow-up were excluded from the main analysis. Allopurinol initiators were classified as current users if their last prescription ended in the 30-day window before the recorded date of AMI for cases and a random date for controls. The association between use of allopurinol and non-fatal AMI was measured through an OR and adjusted for confounding factors by an unconditional logistic regression. Results We identified 3171 cases of non-fatal AMI and 18 525 controls. Cases had a lower prevalence of current use of allopurinol (0.82%) than controls (1.03%), yielding to an OR of 0.52 (95% CI 0.33 to 0.83). The decreased risk was driven by men (OR in men=0.44; 95% CI 0.25 to 0.76; OR in women=0.90; 0.36 to 2.23). No difference by age was observed. The effect was only observed at higher doses (300 mg or greater OR=0.30; 0.13 to 0.72;