Source: DGNews  |  Posted 3 years ago

OTTAWA, Ontario -- January 28, 2009 -- Patients taking clopidogrel following a myocardial infarction (MI) are at a significantly higher risk of a recurrence if they are also taking proton pump inhibitors (PPIs), according to a study published early online and appearing in the March issue of the Canadian Medical Association Journal.

The study, conducted over 6 years in thousands of MI patients aged 66 years and older, found a significantly increased risk of readmission for MIs if patients were taking 1 of several PPIs, including omeprazole, lansoprazole, or rabeprazole. The investigators found no such association with pantoprazole or with other H2 receptor antagonists.

Previous research indicates that PPIs other than pantoprazole can block the liver's ability to convert clopidogrel to its active form -- a critical step required for clopidogrel's anti-platelet effect.

Recent guidelines from the American Heart Association, the American College of Gastroenterology, and the American College of Cardiology recommend PPI therapy for many patients following an MI to prevent bleeding from the stomach, including all patients aged 60 years or older receiving acetylsalicylic acid (ASA). Because clopidogrel and ASA are often prescribed together following an MI, it is probable that millions of patients worldwide will take a PPI with clopidogrel.

"Depending on the exposure to these drugs following a heart attack, we estimate that 5% to 15% of early readmissions for myocardial infarction among patients taking clopidogrel could be the result of this drug interaction," writes Dr. David Juurlink, Head of the Division of Clinical Pharmacology and Toxicology, Sunnybrook Health Sciences Centre, Toronto, Ontario, and lead author of the study, which was conducted at the Institute for Clinical Evaluative Sciences, Toronto, Ontario. "These findings highlight a widely unappreciated, extremely common, and completely avoidable drug interaction in a population of patients at very high risk of reinfarction."

"Our findings suggest that indiscriminate treatment with a proton pump inhibitor could result in thousands of additional cases of recurrent myocardial infarction each year, all of which could be avoided simply by selectively prescribing pantoprazole in patients receiving clopidogrel who require treatment with a proton pump inhibitor," wrote the authors.

SOURCE: Canadian Medical Association Journal