Significance of serum ribavirin concentration in combination therapy of interferon and ribavirin for chronic hepatitis C

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-alpha-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. Copyright (C) 2005 S. Karger AG, Basel.