The antiplatelet drug clopidogrel (Plavix, and others) reduces major cardiovascular events, but can cause bleeding. Proton pump inhibitors (PPIs) are often used with clopidogrel to prevent gastrointestinal bleeding, however, some evidence suggests that PPIs may interfere with the activation of clopidogrel and diminish its antiplatelet effect. FDA-approved labeling recommends avoiding concurrent use of the PPIs omeprazole and esomeprazole with clopidogrel.