Abstract
Chest pain in acute coronary syndrome (ACS) unresponsive to nitrates is routinely treated by intravenous (IV) morphine. In the past two decades, several studies have emerged, suggesting poorer outcomes in patients receiving this treatment; however, morphine remains the drug of choice for these patients as per the American College of Cardiology/American Heart Association guidelines on ACS management. The results of various studies that examined the impact of morphine on myocardial infarct size, antiplatelet therapy absorption time, and patient mortality are discussed. There is mounting evidence suggesting that morphine may increase adverse events in ACS patients, therefore, the development of more precise criteria for IV morphine administration in ACS patients is needed.
Highlights
BackgroundChest pain is the most common presenting complaint in acute coronary syndrome (ACS)
The American College of Cardiology (ACC)/American Heart Association (AHA) guidelines on ACS management endorsed morphine as a Class IC indication for chest discomfort unresponsive to nitrates in ST-segment elevation myocardial infarction (STEMI), non-ST-segment elevation myocardial infarction (NSTEMI), and unstable angina (UA) patients despite a lack of randomized outcome trials to evaluate its safety and efficacy or support this usage [4]. It was not until a 2005 retrospective analysis demonstrating an increased risk of mortality in patients receiving morphine was published that serious concerns were raised and the indication was eventually reduced to a Class IIb recommendation in NSTEMI and UA populations [5]
The analysis showed that patients who were administered morphine prior to primary percutaneous coronary intervention (PCI) had greater myocardial salvage index (MSI), larger infarct sizes, and an increased occurrence of hemorrhagic infarction or microvascular obstruction (MVO)
Summary
Chest pain is the most common presenting complaint in acute coronary syndrome (ACS). The Influence of Morphine on Pharmacokinetics and Pharmacodynamics of Ticagrelor in Patients with Acute Myocardial Infarction (IMPRESSION) trial is a phase IV, single-center, randomized, double-blinded, placebo-controlled study that investigated the influence of morphine on the pharmacokinetics and pharmacodynamics of ticagrelor Ticagrelor is another P2Y12 receptor antagonist considered alongside aspirin to be an essential medication in the long-term management of ACS. This study’s sample size is still not extensive enough to permit a satisfactory assessment of other potential clinical effects of morphine and the use of HRPR as a measurement of platelet inhibition is not ideal, as HRPR is not an equivalent substitution for reduced antiplatelet effect Despite these limitations, this study does improve on both the IMPRESSION trial and the Hobl et al study in its significantly larger enrollment size, which bodes well for the external validity of the findings and makes important contributions to the understanding of morphine’s interactions with antiplatelet agents [7].
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