The safety of morphine use in acute coronary syndrome: a meta-analysis

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.