Impact of Preadmission Morphine on Reinfarction in Patients With ST-Elevation Myocardial Infarction Treated With Percutaneous Coronary Intervention: A Meta-Analysis

Opiates are the traditional analgesics used in patients with ST-elevation myocardial infarction (STEMI). Pharmacodynamic studies indicate that opiates delay the absorption of orally administered P2Y ₁₂ inhibitors and the onset of platelet inhibition. Whether these negative effects on platelet inhibition have an impact on clinical outcomes is unclear. A systematic review and meta-analysis was performed searching PubMed, MEDLINE, and Cochrane Central Register of Controlled Trials to identify studies comparing morphine and no-morphine treatment in STEMI patients undergoing primary percutaneous coronary intervention. The primary end point was the occurrence of in-hospital myocardial infarction, and secondary end points were in-hospital stroke and death. Four observational studies were identified, including 3,220 patients with STEMI. Morphine-treated patients had a higher unadjusted rate of reinfarction compared with patients not receiving morphine (1.5% vs. 0.67%, odds ratio (OR) 2.41; 95% confidence interval (CI), 1.11–5.21; P = 0.03). Unadjusted mortality rate was lower in morphine-treated patients (1.7% vs. 4.2%, OR 0.43, 95% CI, 0.23–0.81; P = 0.009). Exclusion of the study with baseline differences between groups showed more frequent reinfarction in the morphine group, but this was no longer statistically significant (1.3% vs. 0.5%, OR 2.02; 95% CI, 0.39–10.43; P = 0.40). There was no difference in stroke according to morphine treatment. Patients pretreated with morphine appear to have a higher rate of reinfarction than patients not receiving morphine. This may be attributable to opiate-related delay in P2Y ₁₂ inhibitor absorption and resultant delay in onset of platelet inhibition. These concerning findings indicate the need for prospective, randomized trials to assess the impact of opiates on clinical outcomes in STEMI.