3--azido-3--deoxythymidine-5-phosphate and HIV-Seropositivity

AZT concentrations as low as 0.001 mg/l inhibit viral replication, while concentrations above 0.3 mg/l cause considerable damage to erythroid, myeloid progenitor cells and inhibit blastogenesis in mononuclear cells. Furthermore, AZT must be converted first to monophosphate and then to diphosphate and finally to triphosphate by the same enzyme: thymidine kinase (TK). Therefore, large doses of AZT overwhelm TK, causing massive production of monophosphate and reducing the production of di and triphosphate. Yet the recommended dosage of 100 mg AZT every 4 hours results in a peak concentration of 0.5 mg/l and a trough concentration of 0.1 mg/l (harmful to human cells and resulting in reduced production of triphosphate). On the other hand, sublingual administration of 1 mg AZT monophosphate every 8 hours (since the intracellular half life of AZT triphosphate is 3 hours) would be desirable, resulting in more damage to the virus and less harm to the patient. Finally, the small dose of monophosphate ensures that most of the AZT be converted to triphosphate, greatly increasing the efficiency and reducing the likelihood of the virus developing resistance due to reverse transcriptase binding to the similar but non inhibiting mono and diphosphate.

Topics: Administration, Sublingual; Anti-HIV Agents; Dideoxynucleotides; HIV; HIV Infections; HIV Seropositivity; Humans; Models, Biological; Thymidine Kinase; Thymine Nucleotides; Virus Replication; Zidovudine