Drug Interactions Newsletter

Volume 1, Issue 23, 06/23/2009

Question

What is the mechanism by which metronidazole (Flagyl®) causes clinically relevant increases in warfarin (Coumadin®, Jantoven®) blood concentrations and puts the patient at risk for bleeding?

Answer

Warfarin (Coumadin®) is an oral anticoagulant most commonly used for the prevention and treatment of thromboembolic events (blood clots) in patients with atrial fibrillation, prosthetic heart valves, venous thrombosis and/or pulmonary embolism.(1)  Metronidazole (Flagyl) is an oral antibiotic most commonly used to treat a number of gastrointestinal and genitourinary infections.(2-4)

The concern with concurrent therapy is the reporting of clinically significant increases in INR when patients taking warfarin are prescribed metronidazole.(5,6)  Warfarin is....

There is a figure available with this newsletter that shows the drg interaction between metronidazole and warfarin.

Other keywords found in this issue:  cytochrome P450, CYP450, enantiomer, protein binding, drug transporters 

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