Clinical pharmacokinetics of stavudine

Stavudine (d4T) is a pyrimidine nucleoside analogue used in the treatment of human immunodeficiency virus (HIV) infection. It inhibits viral reverse transcriptase as do zidovudine (AZT), didanosine (ddI), zalcitabine (ddC) and lamivudine (3TC), which comprise the family of nucleoside HIV-reverse transcriptase inhibitors. Stavudine is currently approved by the US Food and Drug Administration for the treatment of patients who have become intolerant to or have failed to response to zidovudine, didanosine or zalcitabine therapy. Oral administration of stavudine results in maximal concentrations within 2 hours and increases linearly as doses increase. The absolute oral bioavailability is high, approaching 100%. There is evidence to suggest that stavudine does not accumulate in the plasma. It distributes into total body water and appears to enter cells by non-facilitated diffusion. Penetration into the cerebrospinal fluid occurs, as does the transfer of the drug across human placental tissue. Stavudine is cleared quickly by both renal and nonrenal processes. The pharmacokinetic properties of stavudine in children are similar to those of adults. The pharmacokinetic parameters of stavudine were not affected by simultaneous administration of didanosine. It appears that stavudine at doses < 2 mg/kg/day is most efficient at increasing CD4 + cell numbers. While stavudine is reported to be less cytotoxic than zidovudine, the principal toxicity in humans is peripheral neuropathy and appears to be related to daily, but not cumulative, doses.