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Increased warfarin requirements in a patient with chronic hepatitis C infection receiving sofosbuvir and ribavirin

Purpose A case of increased warfarin requirements during treatment with sofosbuvir and ribavirin for chronic hepatitis C virus (HCV) infection is reported. Summary A 63‐year‐old white man receiving long‐term anticoagulation with warfarin for atrial fibrillation and a history of cardioembolic stroke was initiated in September 2014 on a 12‐week course of sofosbuvir 400 mg orally daily and weight‐based ribavirin 600 mg orally twice daily for HCV genotype 2 infection. Before starting this treatment regimen, the patient had been stable on warfarin 52.5 mg weekly, with therapeutic International Normalized Ratio (INR) values. During the 12‐week course of sofosbuvir and ribavirin, the patient’s dose of warfarin progressively increased from 52.5 to 77.5 mg weekly due to subtherapeutic INRs, with the first adjustment in the warfarin dose occurring 9 days after initiation of HCV treatment. Three weeks after completion of the sofosbuvir and ribavirin regimen, the patient’s INR was 3.06, and his warfarin dose was then decreased to 70 mg weekly. The patient continued with this warfarin dosage until 18 weeks after completion of his HCV regimen. The dosage was then decreased to 65 mg weekly after an INR of 3.86. Three weeks later, his INR was 2.19, and warfarin 65 mg weekly was continued. As of June 2016, the patient has continued to require warfarin 62.5–65 mg weekly to maintain a therapeutic INR. Conclusion A 63‐year‐old man on a stable dose of warfarin experienced a decrease in INR values after the initiation of a 12‐week course of sofosbuvir and ribavirin for the treatment of chronic HCV infection.