Pharmacokinetics and long-term tolerance to ribavirin in asymptomatic patients infected with human immunodeficiency virus.

Single-dose and steady-state pharmacokinetics of the antiviral agent ribavirin were studied in seven male, asymptomatic, human immunodeficiency virus-seropositive subjects. After a single 400 mg intravenous infusion, mean terminal plasma half-life (t1/2) was 27.1 hours, mean volume of distribution was 802 L, and mean total plasma clearance was 26.1 L/hr. Renal clearance was 39% of total clearance and it exceeded creatinine clearance. Oral bioavailability was 44.6%. With long-term dosing (400 mg orally twice a day) ribavirin accumulated, reaching steady state in 2 to 4 weeks in plasma and red blood cells. Red blood cell concentrations greatly exceeded plasma concentrations (60:1). Plasma concentrations at steady state (trough) were 10- to 14-fold higher than the corresponding single-dose concentrations. The terminal t1/2 (washout) after 16 weeks greatly exceeded the t1/2 observed after a single oral dose (151 versus 29.6 hours). Ribavirin-induced reductions in hemoglobin ranging from 0.8 to 3.5 gm/dl were well tolerated. There was no significant reduction in CD4 lymphocytes during treatment with ribavirin for 16 weeks in subjects who had more than 200 CD4 cells at entry and who also remained free of opportunistic infections during 24 weeks of observation.