Background: The very significant benefit of P2Y12 receptor inhibitor administration in patients with ST-elevation myocardial infarction (STEMI), in reducing future ischaemic events and stent thrombosis, is undisputed. Morphine analgesia is very frequently co-administered to these patients for pain relief, along with antiplatelet therapy, at the time of presentation, and prior to reperfusion with primary percutaneous coronary intervention.
Methods: Research and online content related to opiates use in STEMI was reviewed. Bibliographies of retrieved studies were searched manually for additional studies and reviews.
Results: There is sufficient data from pharmacokinetic and pharmacodynamic studies showing that the co-administration of morphine with oral P2Y12 receptor inhibitor results in delayed antiplatelet effects. However, whether this results in adverse outcomes remains unclear. Data from studies reporting the effect of morphine on clinical outcomes in STEMI are inconsistent, although they tend to be underpowered to show an effect on hard clinical outcomes, but some clearly show a relationship between morphine use and infarct size. Strategies to overcome the potentially significant negative impact of morphine on platelet reactivity in STEMI are discussed.
Conclusion: Whilst clearly definitive, adequately powered, randomised controlled trials are lacking, we would recommend avoiding the combination of morphine with oral P2Y12 receptor inhibitors and recommend alternative strategies including intravenous platelet inhibitor strategies, in high risk patients.
Keywords: Opiates, morphine, myocardial infarction, acute coronary syndrome, platelet reactivity, antiplatelet therapy.