Significance of Serum Ribavirin Concentration in Combination Therapy of Interferon and Ribavirin for Chronic Hepatitis C

Abstract

Objective: The purpose of this clinical retrospective cohort study was to determine the most suitable ribavirin concentration on combination therapy of interferon (IFN)-ribavirin. Methods: Entry criteria were serum HCV-RNA level ≧100 KIU/ml, HCV-genotype 1b, chronic hepatitis, and initial combination treatment of IFN-α-2b (6 million units daily for 2 weeks and then 3 times weekly for 6 weeks) and ribavirin (600–800 mg/day) for 8 weeks without stopping or decreasing the dosage of IFN and/or ribavirin. Sixty-eight consecutive patients who satisfied the above criteria were given maintenance therapy for another 16 weeks. Results: A sustained virological response (SVR) rate of 25.0% (17/68) was seen in all subjects. The SVR rate was 44.0% (11/25) in the high ribavirin group with a serum ribavirin concentration of ≧3,000 ng/ml at 8 weeks after initiation of combination therapy. SVR was significantly dependent at a serum ribavirin level of ≧3,000 ng/ml (p = 0.005). The incidence of discontinuations and dose modifications for combination therapy in patients having a serum ribavirin concentration of ≧3,500 ng/ml 8 weeks after initiation of therapy was 57.1% (4/7). This value was statistically higher than that in patents with <3,500 ng/ml (p = 0.033). Conclusion: Our results showed that the most suitable serum ribavirin concentrations are from 3,000 to 3,500 ng/ml 8 weeks after initiation of combination therapy.