Another important clopidogrel interaction

CMAJ reports that proton pump inhibitors (PPIs), which inhibit the cytochrome P450 2C19 enzyme responsible for biotransformation of clopidogrel (Plavix) from prodrug to active drug, cause a clinically significant interaction leading to reduced effectiveness of clopidogrel. The exception among the PPIs appears to be pantoprazole (Protonix). From the article:

Among 13 636 patients prescribed clopidogrel following acute myocardial infarction, we identified 734 cases readmitted with myocardial infarction and 2057 controls. After extensive multivariable adjustment, current use of proton pump inhibitors was associated with an increased risk of reinfarction (adjusted odds ratio [OR] 1.27, 95% confidence interval [CI] 1.03–1.57). We found no association with more distant exposure to proton pump inhibitors or in multiple sensitivity analyses. In a stratified analysis, pantoprazole, which does not inhibit cytochrome P450 2C19, had no association with readmission for myocardial infarction (adjusted OR 1.02, 95% CI 0.70–1.47).

Via Heartwire.

A similar interaction occurs between clopidogrel and some statins which I have previously mentioned here and here. The significance of that interaction has recently been questioned.