Drug interactions between Plavix and Prevacid

GENERALLY AVOID: Coadministration with proton pump inhibitors (PPIs) may reduce the cardioprotective effects of clopidogrel. The proposed mechanism is PPI inhibition of the CYP450 2C19-mediated metabolic bioactivation of clopidogrel. This is consistent with studies that reported decreased effectiveness of clopidogrel and poorer clinical outcome in patients who have common genetic polymorphisms of CYP450 2C19 resulting in reduced or absent enzyme activity. In a population-based nested case-control study among patients aged 66 years or older who started clopidogrel after treatment of acute myocardial infarction, concomitant use of PPIs was associated with a significantly increased short-term risk of reinfarction. No association was found with more distant exposure to PPIs or with current exposure to H2-receptor antagonists. In a stratified analysis of the type of PPIs used, pantoprazole was not associated with recurrent myocardial infarction among patients receiving clopidogrel. However, the number of patients receiving pantoprazole in the study was relatively small. Compared with no treatment, the other proton pump inhibitors (lansoprazole, omeprazole, rabeprazole) were collectively associated with a 40% increase in the risk of recurrent myocardial infarction within 90 days of initial hospital discharge. In the Clopidogrel Medco Outcomes Study, a retrospective analysis of 16,690 patients taking clopidogrel for a full year following coronary stenting revealed that patients who also took a PPI (esomeprazole, lansoprazole, omeprazole, or pantoprazole) for an average of nine months experienced a 50% increase in the combined risk of hospitalization for heart attack, stroke, unstable angina, or repeat revascularization. Specifically, use of a PPI was associated with a 70% increase in the risk of heart attack or unstable angina, a 48% increase in the risk of stroke or stroke-like symptoms, and a 35% increase in the need for a repeat coronary procedure. The event rates for the individual PPIs are esomeprazole 24.9%, lansoprazole 24.3%, omeprazole 25.1%, and pantoprazole 29.2%, compared to 17.9% for the no-PPI control group. In a study of 105 consecutive high-risk coronary angioplasty patients receiving aspirin and clopidogrel, PPI users had a significantly lower antiplatelet response to clopidogrel than nonusers as measured by the VASP (vasodilator-stimulated phosphoprotein) phosphorylation assay, which provides an index of platelet reactivity to clopidogrel. No significant differences in antiplatelet response were found for users of statins, ACE inhibitors, angiotensin II receptor antagonists, and beta-blockers compared to nonusers. A subsequent study conducted by the same investigators reported similar results when omeprazole (20 mg/day) or placebo was given for seven days to 140 coronary artery stent patients receiving aspirin and clopidogrel. In contrast, a study of 300 consecutive patients with coronary artery disease undergoing PCI found that esomeprazole or pantoprazole use did not impair the response to clopidogrel as measured by VASP assay or ADP-induced platelet aggregometry. Another study also found no effect of lansoprazole on the pharmacokinetics or pharmacodynamics of clopidogrel, and that increasing gastric pH did not influence platelet inhibition by clopidogrel. The interaction has not been studied with dexlansoprazole. According to the product labeling, dexlansoprazole is unlikely to inhibit CYP450 2C19 based on data from in vitro studies. However, it is a substrate of the isoenzyme, thus competitive inhibition could occur.

MANAGEMENT: Until further data are available, patients treated with clopidogrel should preferably avoid the use of proton pump inhibitors. H2-receptor antagonists or antacids should be considered whenever possible.