To explore the effects of morphine on P2Y₁₂ platelet inhibitors in patients with acute myocardial infarction (AMI).

PubMed, Embase, Cochrane Library, and Web of Science were used to retrieve literature through 11th May 2019. Standardized weighted mean difference (SMD) and relative risk (RR) with 95% confidence intervals (CI), P-value, and I² value were used to assess the strength of the association in this meta-analysis. Outcomes included platelet reactivity, high residual platelet reactivity (HRPR), ticagrelor maximum concentration (Cmax), ticagrelor area under curve (AUC), death rate, reinfarction rate, stroke, stent thrombosis, thrombolysis in myocardial infarction (TIMI) hemorrhage, dyspnea, emesis, contrast-induced nephropathy, and pulmonary edema.

A total of 13 articles were included in this study, containing 5688 patients (morphine group: n = 2014, control group: n = 3674). Results illustrated that the morphine group had a higher platelet reactivity (SMD: 0.834, 95%CI: 0.483–1.186, P < 0.001) and HRPR rate (RR: 1.994, 95%CI: 1.536–2.588, P < 0.001) than the control group, while the Cmax of ticagrelor (WMD: -481.838, 95%CI: −841.242–122.434, P = 0.009) was lower than that of the control group. The death rate of the morphine group was lower than that in the control group (RR: 0.561, 95%CI: 0.337–0.933, P = 0.026). The morphine group had a higher emesis rate than the control group (RR: 4.486, 95%CI: 2.263–8.891, P < 0.001).

Morphine effectively suppresses the inhibition effect of P2Y₁₂ platelet inhibitors in patients with AMI.