Zalcitabine

Zalcitabine acts by competitive inhibition of HIV-1 reverse transcriptase. It requires intracytoplasmic activation via phosphorylation by cellular enzymes to its triphosphate form. Its incorporation into the growing viral DNA chain causes chain termination due to inhibition of binding with the incoming nucleotide.

Adult

or 500 mg once then 250 mg bid × 2 days2 Valacyclovir, oral1 1000 mg bid × 7­10 days 500 mg bid × 3 days 500–1000 mg2 or 1 g qd × 5 days Orolabial herpes Acyclovir, oral1 400 mg tid × 7–10 days 400 mg tid × 5 days 400 mg bid2 or 200 mg 5 times daily Famciclovir, oral1 250 mg tid or 500 mg bid × 7–10 days 1500 mg once or 750 mg bid × 1 day 500 mg bid Valacyclovir, oral1 1 g bid × 7–10 days 2 g bid…

• No longer marketed worldwide due to suboptimal safety, inferior efficacy, high pill burden, or pharmacologic concerns