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CLINICAL RESEARCH: CLINICAL TRIAL

Influence of Omeprazole on the Antiplatelet Action of Clopidogrel Associated With Aspirin

The Randomized, Double-Blind OCLA (Omeprazole CLopidogrel Aspirin) Study

Martine Gilard, MD^_*,_*, Bertrand Arnaud, PharmD, Jean-Christophe Cornily, MD^_*, Grégoire Le Gal, MD, Karine Lacut, MD, Geneviève Le Calvez, PharmD, Jacques Mansourati, MD^_*, Dominique Mottier, MD, Jean-François Abgrall, MD^,1 and Jacques Boschat, MD^_*,1

^_* Department of Cardiology, Brest University Hospital, Brest, France
Department of Hematology, INSERM 0502, Brest University Hospital, Brest, France
Center for Clinical Investigation, EA3878, Brest University Hospital, Brest, France
Department of Internal Medicine and Chest Diseases, Brest University Hospital, Brest, France.

Manuscript received March 19, 2007; revised manuscript received June 7, 2007, accepted June 12, 2007.

^_* Reprint requests and correspondence: Dr. Martine Gilard, Département de Cardiologie, CHU de la Cavale Blanche, Boulevard Tanguy Prigent, 29609 Brest Cédex, France. (Email: martine.gilard{at}chu-brest.fr).

Objectives: This trial sought to assess the influence of omeprazole on clopidogrel efficacy.

Background: Clopidogrel has proved its benefit in the treatment of atherothrombotic diseases. In a previous observational study, we found clopidogrel activity on platelets, tested by vasodilator-stimulated phosphoprotein (VASP) phosphorylation, to be diminished in patients receiving proton pump inhibitor (PPI) treatment.

Methods: In this double-blind placebo-controlled trial, all consecutive patients undergoing coronary artery stent implantation received aspirin (75 mg/day) and clopidogrel (loading dose, followed by 75 mg/day) and were randomized to receive either associated omeprazole (20 mg/day) or placebo for 7 days. Clopidogrel effect was tested on days 1 and 7 in both groups by measuring platelet phosphorylated-VASP expressed as a platelet reactivity index (PRI). Our main end point compared PRI value at the 7-day treatment period in the 2 groups.

Results: Data for 124 patients were analyzed. On day 1, mean PRI was 83.2% (standard deviation [SD] 5.6) and 83.9% (SD 4.6), respectively, in the placebo and omeprazole groups (p = NS), and on day 7, 39.8% (SD 15.4) and 51.4% (SD 16.4), respectively (p < 0.0001).

Results: Omeprazole significantly decreased clopidogrel inhibitory effect on platelet P2Y12 as assessed by VASP phosphorylation test. Aspirin-clopidogrel antiplatelet dual therapy is widely prescribed worldwide, with PPIs frequently associated to prevent gastrointestinal bleeding. The clinical impact of these results remains uncertain but merits further investigation. (OCLA: Influence of Omeprazole on the Antiplatelet Action of Clopidogrel Associated to Aspirin; http://www.clinicaltrials.gov/ct2/show/NCT00349661; NCT00349661 [ClinicalTrials.gov] )

Abbreviations and Acronyms   ADP = adenosine diphosphate   MFI = mean fluorescence intensity   PPI = proton pump inhibitor   PRI = platelet reactivity index   SD = standard deviation   VASP = vasodilator-stimulated phosphoprotein

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