Pharmacokinetics of orally administered zidovudine among patients with hemophilia and asymptomatic human immunodeficiency virus (HIV) infection.

Zidovudine (formerly azidothymidine, AZT) is used to treat certain patients infected with the human immunodeficiency virus (HIV). However, the clinical use of zidovudine (ZDV) in hemophilia patients may be complicated by the high incidence of chronic hepatitis in this patient population. To examine the pharmacokinetics of ZDV eight asymptomatic HIV-infected hemophilia patients received a single oral dose (300 mg). ZDV and its glucuronide metabolite (GZDV) were measured in serum by HPLC. ZDV was rapidly absorbed with a wide range of peak serum concentrations (2052 +/- 970 ng/ml) at 0.5 h. Peak GZDV serum concentrations were 4751 +/- 2269 ng/ml at 1 h. Both ZDV and GZDV declined in a biexponential manner over 4 h. After 4 h, the ZDV serum concentration decay in three patients continued a log-linear decline, while five patients demonstrated a tri-exponential curve which had a mean terminal elimination half-life of 4.8 +/- 2.8 h. No relationship between ZDV or GZDV kinetics and the degree of hepatic enzyme elevation was observed. Although a therapeutic window for ZDV has yet to be described, the wide range of serum concentrations that result from a standard dose suggests that clinical monitoring of ZDV levels may be of value in certain patients. In addition, the prolonged elimination half-life of ZDV in the present study may provide a rationale for less frequent dosing in certain patients.