FRIDAY, Dec. 20, 2013 (HealthDay News) -- Morphine interaction reduces the effectiveness of clopidogrel, according to a small study published online Dec. 4 in the Journal of the American College of Cardiology.
Eva-Luise Hobl, Ph.D., from the Medical University of Vienna, and colleagues conducted a randomized, double-blind, placebo-controlled, cross-over trial in which 24 healthy subjects were given a loading dose of 600 mg clopidogrel along with placebo or 5 mg morphine intravenously. Liquid chromatography tandem mass spectrometry was used to determine pharmacokinetics. Platelet function tests measured clopidogrel effects.
The researchers found that morphine significantly delayed clopidogrel resorption (P = 0.025) and reduced the area under the curve levels of its active metabolite by 52 percent (P = 0.001). Two hours was the average delay in maximal inhibition of platelet aggregation with morphine (24 patients; P > 0.001). For one to four hours after morphine injection, residual platelet aggregation was higher (24 patients; P > 0.005). Morphine also delayed platelet plug formation inhibition under high shear rates (21 patients; P > 0.004). In extensive and rapid metabolizers, morphine abolished the three-fold prolongation in collagen adenosine diphosphate induced closure times (16 patients; P = 0.001).
"Morphine delays clopidogrel resorption, decreases plasma levels of clopidogrel active metabolite, retards and diminishes its effects, which can lead to treatment failure in susceptible individuals," Hobl and colleagues conclude.