Morphine may dull antiplatelet loading in STEMI patients

Treating pain with morphine may slow down oral antiplatelet therapy in STEMI patients. The odds of high residual platelet reactivity were nearly three times higher for patients taking morphine two hours after administration of oral antiplatelet therapy.

The analysis included 300 primary PCI patients collected from five source studies.  The research team led by Guido Parodi, MD, PhD, of the Department of Heart and Vessels at Careggi University Hospital in Florence, Italy, reviewed the past cases to determine the action of morphine on the onset of anticoagulation. Thirty-two percent of patients in the study received morphine. Assessments of residual platelet activity occurred at one, two and four hours following loading dose.

Parodi et al found that in addition to more than five times higher vomiting rates, patients given morphine had high levels of P2Y12 reactivity at two hours after antiplatelet dosing. Differences between patients with and without morphine remained after adjusting for vomit. High residual platelet reactivity remained at two hours in 53 percent of patients given morphine, but only 29 percent of patients who were not.

Both morphine and age were independent predictors for the likelihood of high residual platelet reactivity (odds ratio: 2.91 vs 1.03, respectively).

“The morphine–antiplatelet agent interaction is likely a non drug-specific phenomena and related to the inhibition of the normal muscular activity of the stomach and the intestines, which may lead to vomit or delayed gastric emptying, which in turn delays absorption and decreases peak plasma levels of orally administered drugs,” wrote Parodi et al.

The study was published in the January issue of Circulation: Cardiovascular Interventions.