Clopidogrel is routinely prescribed in combination with aspirin after an acute coronary event or percutaneous coronary intervention to reduce reinfarction and prevent in-stent thrombosis. Many patients who need dual antiplatelet treatment are also prescribed proton pump inhibitors, such as omeprazole. Previously the coprescription of these drugs seemed innocuous and was advocated in the American Heart Association/American College of Cardiology Foundation ACCF guidelines,1 but investigation of platelet activity and some large retrospective registry studies have suggested that proton pump inhibitors interact with clopidogrel to attenuate its antiplatelet effects.2 3 This interaction may be clinically important given the widespread prescription of proton pump inhibitors and the nature of coronary artery disease. Yet questions regarding the presence and size of a clinical effect have left prescribers confused about the safety of coprescription and whether other strategies should be considered. Some of these concerns may be resolved by the recent publication of the first international randomised, double blind, double dummy placebo controlled trial …