The EU Committee for Medicinal Products for Human Use (CHMP) has recently considered the available evidence for an interaction between clopidogrel and proton pump inhibitors (PPIs). They concluded that PPIs reduce the effectiveness of clopidogrel in preventing the recurrence of adverse cardiac events such as heart attack and coronary artery restenosis (renarrowing of the artery wall despite past heart surgery). Further information, including a series of questions and answers for patients, is provided below. The European Medicines Agency (external link) has also recently published information on this interaction. Information and advice for healthcare professionals is also published in the July issue of Drug Safety Update on page 2. Clopidogrel Clopidogrel (brand name Plavix) is used to prevent atherothrombotic events (e.g. a heart attack or stroke) in patients who have previously had one of these life-threatening events, or in at-risk patients who have peripheral arterial disease (narrowing of the arteries, mainly in the legs). In combination with aspirin, it can also be used to prevent atherothrombotic events in patients with acute coronary syndrome (a serious disorder with various clinical signs that suggest the heart is receiving inadequate oxygen). PPIs PPIs are used to treat the gastrointestinal disorders, oesophageal reflux disease (a frequent cause of indigestion and heartburn), dyspepsia (indigestion) or gastric ulcers. In the UK, five PPIs are available on prescription: omeprazole, esomeprazole, pantoprazole, rabeprazole, and lansoprazole. Omeprazole is also available over the counter (Losec). Clopidogrel can cause side effects on the gastrointestinal system and is therefore frequently prescribed together with a PPI. Interaction Several studies have found that the use of PPIs lowered the clinical effectiveness of clopidogrel in preventing the recurrence of atherothrombotic events in patients who have previously had a serious heart condition (including coronary artery restenosis or heart attack).