(HealthDay News) — There is a probable interaction between paritaprevir/ritonavir/ombitasvir+dasabuvir (PrOD) plus ribavirin with warfarin, according to a case report published online Nov. 3 in the Journal of Clinical Pharmacy and Therapeutics.
Gina M. Puglisi, Pharm.D., from VA Maine Healthcare System in Augusta, and colleagues present the case of a probable interaction between PrOD with ribavirin and warfarin in a 58-year-old with hepatitis C virus genotype 1a, who was treatment naive. The patient took outpatient medications, including warfarin for stroke risk reduction. The patient was initiated on PrOD with ribavirin for 12 weeks for hepatitis treatment.
The authors note that the patient’s international normalized ratio (INR) became subtherapeutic two weeks after the start of PrOD with ribavirin. Therapeutic INR was achieved 11 weeks into therapy and following a 125 percent total increase in the weekly warfarin dose. The patient’s INR became critically supratherapeutic 13 days after completion of direct-acting antiviral therapy was completed and discontinued. A score of +7 was obtained using the Naranjo Nomogram, which indicated that the increase in INR for warfarin produced by PrOD with ribavirin was probable.
“Patients on PrOD plus ribavirin with warfarin should have INR followed closely upon initiation and discontinuation of therapy due to a probable drug interaction,” the authors write.