Morphine and Cardiovascular Outcomes Among Patients With Non-ST-Segment Elevation Acute Coronary Syndromes Undergoing...

Mechanistic studies have shown that morphine blunts the antiplatelet effects of oral adenosine diphosphate receptor blockers. However, the clinical relevance of this interaction is controversial.

This study sought to explore the association between morphine and ischemic events in 5,438 patients treated with concomitant clopidogrel presenting with non-ST-segment elevation acute coronary syndromes (NSTEACS) in the EARLY ACS (Early Glycoprotein IIb/IIIa Inhibition in Patients With Non-ST-Segment Elevation Acute Coronary Syndrome) trial. Patients not treated with clopidogrel (n = 3,462) were used as negative controls.

Endpoints were the composite of death, myocardial infarction (MI), recurrent ischemia, or thrombotic bailout at 96 h (4-way endpoint) and the composite of death or MI at 30 days.

In patients treated with clopidogrel, morphine use was associated with higher rates of the 4-way endpoint at 96 h (adjusted odds ratio [OR]: 1.40; 95% confidence interval [CI]: 1.04 to 1.87; p = 0.026). There was a trend for higher rates of death or MI at 30 days (adjusted OR: 1.29; 95% CI: 0.98 to 1.70; p = 0.072), driven by events in the first 48 h (adjusted hazard ratio: 1.54; 95% CI: 1.07 to 2.23; p = 0.021). In patients not treated with clopidogrel, morphine was not associated with either the 4-way endpoint at 96 h (adjusted OR: 1.05; 95% CI: 0.74 to 1.49; p = 0.79; p_interaction = 0.36 ) or death or MI at 30 days (adjusted OR: 1.07; 95% CI: 0.77 to 1.48; p = 0.70; p_interaction = 0.46).

When used concomitantly with clopidogrel pre-treatment, morphine was associated with higher rates of ischemic events in patients with NSTEACS. (EARLY ACS: Early Glycoprotein IIb/IIIa Inhibition in Patients With Non-ST-Segment Elevation Acute Coronary Syndrome; NCT00089895).