Abstract
Background Morphine is widely used for pain control in patients with acute coronary syndrome (ACS). Several studies have questioned the safety of morphine in this setting with a concern of interaction with and reduced efficacy of antiplatelet agents. Objective This study aims to systematically review the safety of morphine use in ACS. Methods MEDLINE, EMBASE and the Cochrane Central Register of Controlled Trials were queried from inception through April 2018. Studies comparing morphine to nonmorphine use in ACS were included. Study endpoints included: In-hospital myocardial infarction (MI), all-cause mortality, stroke, major bleeding, minor bleeding and dyspnoea. Results A total of 64 323 patients with ACS were included from eight studies, seven of which were observational studies and one was a randomised controlled trial. The use of morphine was associated with increased risk of in-hospital recurrent MI (OR 1.30, 95% CI 1.18 to 1.43, p < 0.00001). There was, however, no significant difference in terms of all-cause mortality (OR 0.87, 95% CI 0.62 to 1.22, p = 0.44), stroke (OR 0.81, 95% CI 0.39 to 1.66, p = 0.57), major bleeding (OR 0.49, 95% CI 0.24 to 1.00, p = 0.05), minor bleeding (OR 0.98, 95% CI 0.41 to 2.34, p = 0.97), or dyspnoea (OR 0.55, 95% CI 0.16 to 1.83, p = 0.33). Conclusion The use of morphine for pain control in ACS was associated with an increased risk of in-hospital recurrent MI. Randomised clinical trials are needed to further investigate the safety of morphine in ACS.