Ribavirin and abacavir drug interaction in HIV-HCV coinfected patients: fact or fiction?

OBJECTIVE(S) To examine the impact of ribavirin and abacavir coadministration on hepatitis C virus (HCV) virological response and trough ribavirin plasma concentration (Cmin) in HIV-HCV coinfected patients. DESIGN Pharmacokinetic substudy on patients from the ANRS CO-13 HEPAVIH cohort. METHODS Patients receiving ribavirin-pegylated interferon for whom a ribavirin steady state Cmin was prospectively determined were included. Rapid virological response (RVR), early virological response (EVR) and sustained virological response (SVR) as well as HCV-RNA decline were evaluated. RESULTS Overall, 124 HIV-HCV coinfected patients (95% on antiretroviral therapy) were enrolled. Of these patients, 22% received abacavir. The overall median (interquartile range) ribavirin Cmin was 1.6 mg/l (1.2-2.2) with no statistical difference between abacavir users and nonusers [1.5 mg/l (0.99-2.1) and 1.7 (1.2-2.3), P = 0.15]. RVR and EVR were 52 and 72%, respectively. There was no difference observed in the proportion of abacavir users vs. nonusers achieving RVR (respectively 59 vs. 50%, P = 0.40) or EVR (72 vs. 73%, P = 0.94), or in the HCV-RNA decline at week 4 [-2.24 log(10) IU/ml, (-3.58; -0.81) and -1.27 (-2.8; -0.47) P = 0.28] or at week 12 [-1.76 log(10) IU/ml (-3.67; -0.35) and -1.85 (-3.13; -1.13) (P = 0.58)]. The SVR rate was 45% for abacavir users and 24% for abacavir nonusers, but the difference was not statistically significant (P = 0.059). CONCLUSION In our study, there was no evidence that abacavir affected HCV treatment outcomes and the ribavirin Cmin was similar in abacavir users and nonusers, confirming the absence of pharmacokinetic interaction between abacavir and ribavirin. An abacavir-containing regimen is, therefore, a well tolerated treatment alternative for coinfected patients starting HCV treatment.