Background A recent pooled analysis of randomised trials found an increased risk of myocardial infarction with use of the antiosteoporotic drug strontium ranelate. We conducted a nationwide cohort study in Denmark, 2005–2011, to investigate the risk of acute coronary syndrome among postmenopausal women treated with strontium ranelate.

Methods The study involved two analytic setups. The first analysis included new users of either strontium ranelate (n=1798) or one of the two first-line bisphosphonates in Denmark (alendronate and risedronate; n=65 236). The second analysis included patients who had first been treated with a first-line bisphosphonate and subsequently switched to either strontium ranelate (n=1219) or ibandronate (n=2290). The primary outcome was acute coronary syndrome (unstable angina or myocardial infarction). The secondary outcome was any-cause mortality. Cox regression was used to estimate HRs, with adjustment using a disease risk score.

Results Compared with use of alendronate/risedronate, use of strontium was not associated with significantly increased risk of acute coronary syndrome (rate per 1000 person-years 5.7 for strontium vs 6.3 for alendronate/risedronate; adjusted HR 0.89, 95% CI 0.52 to 1.55) or any-cause mortality (adjusted HR 0.96, 95% CI 0.76 to 1.21). In the analysis of switchers, strontium was not associated with significantly increased risk of acute coronary syndrome (rate per 1000 person-years 9.9 for strontium vs 9.9 for ibandronate; adjusted HR 1.00, 95% CI 0.49 to 2.05) or of any-cause mortality (adjusted HR 1.45, 95% CI 0.95 to 2.21).

Interpretation These real-world data of antiosteoporotic drug users do not support a significant association between use of strontium ranelate and acute coronary syndrome.