Zalcitabine Zalcitabine was originally approved in combination with AZT in patients with no prior antiretroviral experience. Current recommendations generally advise a three-drug combination including a protease inhibitor. HIV strains with decreased in vitro susceptibility to zalcitabine have been isolated from patients on long term zalcitabine therapy. Results of some in vitro studies show that AZT -resistant HIV strains are still susceptible to zalcitabine, and vice versa. Cross-resistance between zalcitabine and HIV protease inhibitors is unlikely because the drugs target different enzymes.
Zalcitabine is well absorbed following oral administration.
Food in the GI tract may decrease the extent of absorption. Peak plasma concentrations in adults are attained in 0.5-2 hours. It is not known whether the drug is distributed in milk. The drug is not metabolized substantially in the liver. Zalcitabine is eliminated principally in urine.