Warfarin Institute of America
Dedicated To Your Health
VORICONAZOLE INTERACTIONS WITH WARFARIN
Brand Name: V-Fend
This is an antifungal that is similar to fluconazole and it is metabolized by the same liver enzymes. For this reason, it should be expected that it will have a very potent interaction with warfarin. For a hospitalized patient, it would be wise to check the INR daily. For an outpatient, it would be wise to check the INR about 3 to 5 days after voriconazole is added to warfarin. Likewise, downward dosage adjustments will likely be necessary when voriconazole is stopped and warfarin is continued. As of this date, there no indications of how long the onset or offset of the interaction will take, the effect of fluconazole is seen rather quickly. The INR should be monitored until it is stable for several days for an in-patient and for two successive readings for an outpatient.
I originally posted the above in May 2002. Finally nineteen months later the results of a study were published in a medical journal confirming that this does happen.
I have not been able to find any reports in medical journals showing that anyone has actually suffered harm from this interaction, but the potential exists.
References:
Bulletin of The Hong Kong Society for Infectious Diseases
- Purkins L, Wood N, Kleinermans D, Nichols D. Voriconazole potentiates warfarin-induced prothrombin time prolongation. Br J Clin Pharmacol. 2003 Dec;56 Suppl 1:24-9.
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This reaction also happens with other members of this family: econazole, fluconazole, itraconazole, metronidazole, and miconazole.
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Last updated November 27, 2004