Pharmacokinetics of azidothymidine and its major metabolite glucuronylazidothymidine in hemophiliacs coinfected with human immunodeficiency virus and chronic hepatitis C

The increasingly reported cholestatic course of liver disease in hemophiliacs coinfected with human immunodeficiency virus (HIV) and hepatitis C (HCV) has been linked with impaired azidothymidine (AZT) metabolism in this patient group. Therefore, we compared the pharmacokinetics of AZT and its glucuronidated metabolite (glucuronylazidothymidine [GAZT]) in HIV/HCV-coinfected hemophiliacs without cirrhosis to HIV-infected patients without chronic hepatitis. Sixteen HIV/HCV-coinfected hemophiliacs without cirrhosis and six HIV-infected patients with negative hepatitis serology and normal liver transaminases received a single 100-mg oral dose of AZT. Subsequently, plasma concentrations of AZT and GAZT were measured during a 6-hour period by high-pressure liquid chromatography (HPLC). Blood samples were taken before and 30, 60, and 90 minutes and 2, 3, 6, and 8 hours after the intake of AZT. Pharmacokinetic parameters of AZT in HIV-infected patients with concomitant chronic hepatitis did not differ significantly as compared to patients without concomitant liver disease. GAZT half-life and mean residence time of GAZT, however, were significantly longer in HIV/HCV-coinfected hemophiliacs as compared to HIV-positive controls without hepatitis. In HIV-infected patients, underlying chronic hepatitis C does not require AZT dose adaptation. Yet despite normal oral clearance of AZT and GAZT, the increase of half-life and mean residence time of GAZT indicates a prolonged hepatic release of GAZT into the circulation of HIV-infected hemophiliacs with noncirrhotic hepatitis C.