ABSTRACT
<p><b>BACKGROUND</b>Omeprazole, usually used in the antiplatelet therapy during percutaneous coronary intervention (PCI) in acute coronary syndrome (ACS), has been reported to increase ischemic events in retrospective studies. However, other clinical trials gave paradoxical results. The aim of this study was to assess the effects of omeprazole on clopidogrel efficacy and clinical events.</p><p><b>METHODS</b>All patients (n = 172) received aspirin (loading dose 300 mg and maintenance dose 100 mg/d) and clopidogrel (loading dose 600 mg and maintenance dose 75 mg/d) during the therapy. They were randomized to receive omeprazole (20 mg/d) or placebo for 30 days. Residual platelet activities in the adenosine 5'-diphosphate (ADP) pathway were detected on the fifth day after PCI with thrombelastography (TEG)-mapping. The clinical events were recorded after one month.</p><p><b>RESULTS</b>According to the five levels of platelet activities, the frequency distributions of the inhibition rates were significantly different (P = 0.0062). However, no significant change was seen in the distribution among the highest or the lowest inhibiting levels (> 95% and < 30% inhibition rate). And there were no significant differences (P > 0.05) in events incidence, while gastro-intestinal bleeding decreased in co-administration of omeprazole.</p><p><b>CONCLUSIONS</b>Omeprazole significantly blunts clopidogrel efficacy while not exacerbates ischemic events in ACS undergoing PCI. Omeprazole even can decrease gastro-intestinal bleeding in those patients.</p>