To quantify the risk of non-fatal acute myocardial infarction (AMI) among users of allopurinol.
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.
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; <300 mg OR=0.67; 0.37 to 1.23) and with prolonged treatments (<31 days, OR=1.12 (0.55 to 2.29); 31-180 days, OR=0.61; 0.29 to 1.29; >180 days OR=0.21; 0.08 to 0.53; p for trend=0.001). Among those with a previous AMI, allopurinol use also showed a significant reduced risk of recurrence (OR=0.16; 0.04 to 0.76).
The present study supports the hypothesis that allopurinol is associated with a reduced risk of non-fatal AMI, which seems to be dose-dependent and duration-dependent.