Pharmacodynamic evaluation of clopidogrel plus PA32540: The spaced PA32540 with clopidogrel interaction gauging (SPACING) study

PA32540 combines 325 mg enteric-coated (EC) aspirin (ASA) with 40 mg immediate-release omeprazole; its influence on the antiplatelet effect of clopidogrel (C) is unknown. In this randomized, open-label study, subjects (n = 30) were treated with (i) 300 mg C + 325 mg ECASA followed by 75 mg C + 325 mg ECASA on days 2-7, (ii) 300 mg C + PA32540 followed by 75 mg C + PA32540 on days 2-7, or (iii) PA32540 in the morning 300 mg C + 10 h later on day 1 and PA32540 in the morning 75 mg C + 10 h later on days 2-7. We analyzed the noninferiority of PA32540 relative to ECASA, as defined by the upper bound of the 95% confidence interval ≤10% for the difference in least-square means of platelet inhibition between the treatments. As compared to ECASAC, synchronous treatment of PA32540+C was not noninferior, whereas the spacing strategy of PA32540+C was noninferior. Spacing the administration of PA32540 and clopidogrel lessens the interaction observed with synchronous administration; PA32540 administration with clopidogrel may be associated with a different antiplatelet profile.