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Zalcitabine


ACCESSION NB: DB00943 (APRD00562)


TYPE: small molecule


GROUP: approved


DESCRIPTION:
A dideoxynucleoside compound in which the 3’-hydroxyl group on the sugar moiety has been replaced by a hydrogen. This modification prevents the formation of 5’ to 3’ phosphodiester linkages, which are needed for the elongation of DNA chains, thus resulting in the termination of viral DNA growth. The compound is a potent inhibitor of HIV replication at low concentrations, acting as a chain-terminator of viral DNA by binding to reverse transcriptase. Its principal toxic side effect is axonal degeneration resulting in peripheral neuropathy. [PubChem]

VOLUME OF DISTRIBUTION: 0.304 to 0.734 L/kg

CATEGORIES:
Anti-HIV Agents Antimetabolites Nucleoside and Nucleotide Reverse Transcriptase Inhibitors Reverse Transcriptase Inhibitors

ABSORPTION: Bioavailability is over 80% following oral administration.

INDICATION:
For the treatment of Human immunovirus (HIV) infections in conjunction with other antivirals.

PHARMACODYNAMICS:
Zalcitabine is an analog of 2'-deoxycytidine that is pharmacologically related to but structurally different from other nucleotide reverse transcriptase inhibitors (NRTIs). Zalcitabine inhibits the activity of HIV-1 reverse transcriptase (RT) both by competing with the natural substrate dGTP and by its incorporation into viral DNA.

MECHANISM OF ACTION:
Zalcitabine is a nucleoside reverse transcriptase inhibitor (NRTI) with activity against Human Immunodeficiency Virus Type 1 (HIV-1). Within cells, zalcitabine is converted to its active metabolite, dideoxycytidine 5'-triphosphate (ddCTP), by the sequential action of cellular enzymes. ddCTP interferes with viral RNA-directed DNA polymerase (reverse transcriptase) by competing for utilization of the natural substrate deoxycytidine 5'-triphosphate (dCTP), as well as incorpating into viral DNA. Due to it's lack of a 3'-OH group, the formation of a 5' to 3' phosphodiester linkage that is necessary for DNA chain elongation is inhibited, thus leading to the termination of viral DNA growth.

PROTEIN BINDING:
Less than 4%

METABOLISM:
Hepatic

TOXICITY:
Acute overdose: Inadvertent pediatric overdoses have occurred with doses up to 1.5 mg/kg zalcitabine. Chronic overdose: in an initial dose-finding study in which zalcitabine was administered at doses 25 times (0.25 mg/kg every 8 hours) the currently recommended dose, one patient discontinued zalcitabine after 11⁄2 weeks of treatment subsequent to the development of a rash and fever.

AFECTED ORGANISMS:
Human Immunodeficiency Virus