Azithromycin and Warfarin Interaction

Mechanism of Interaction

Azithromycin may potentiate warfarin's effects through alteration of the gut microbiome, which is a source of vitamin K, thereby enhancing warfarin's anticoagulant effects 3
Unlike other macrolides, azithromycin does not significantly inhibit the cytochrome P450 system, making it the preferred macrolide when co-administration with warfarin is necessary, according to the Centers for Disease Control and Prevention, as stated in MMWR Recommendations and Reports 4

The American Geriatrics Society recommends close monitoring of INR values due to potential increased bleeding risk when azithromycin is used with warfarin, as stated in the Journal of the American Geriatrics Society 1
The British Association of Dermatologists' guidelines list warfarin as having a documented interaction with azithromycin, noting "warfarin resistance is reported and warfarin dose may need to be increased, close monitoring of anticoagulation is advised" 5

Elderly patients may be at higher risk for drug interactions due to polypharmacy, according to the British Association of Dermatologists 5