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Zidovudine phosphorylation after short‐term and long‐term therapy with zidovudine in patients infected with the human immunodeficiency virus
Author(s) -
Peter Katrin,
Gambertoglio John G.
Publication year - 1996
Publication title -
clinical pharmacology and therapeutics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.941
H-Index - 188
eISSN - 1532-6535
pISSN - 0009-9236
DOI - 10.1016/s0009-9236(96)90132-0
Subject(s) - zidovudine , reverse transcriptase inhibitor , sida , virology , thymidine , pharmacology , medicine , biology , immunology , viral disease , virus , biochemistry , in vitro
Background Resistance of human immunodeficiency virus (HIV) to zidovudine (AZT) has been associated with mutations in the viral reverse transcriptase gene. However, recent studies suggest that host cellular factors such as a decreased thymidine kinase activity or an increased cellular P‐glycoprotein expression may be important. This study compared concentrations of zidovudine monophosphate, zidovudine diphosphate, and zidovudine triphosphate with P‐glycoprotein expression in peripheral blood mononuclear cells from patients receiving long‐term (> 18 months) and short‐term (<2 months) zidovudine treatment. Methods Ten subjects in the short‐term group and 11 subjects in the long‐term group with CD4 counts between 300 and 500 received a single oral dose of zidovudine (200 mg) after a 24‐hour washout period. Blood samples were collected at 0, 1, 2, 4, and 6 hours. Intracellular nucleotide concentrations were measured by a combined HPLC‐radioimmunoassay method, and P‐glycoprotein expression was determined by fluorescence activated cell sorting (FACS) analysis with use of the monoclonal mouse antibody MRK‐16. Results Zidovudine monophosphate was the predominant compound, accounting for 73.4% ± 7.1% (SD) of the total phosphates in the long‐term treatment group and 74.2% ± 15.0% (SD) in the short‐term group. Zidovudine diphosphate accounted for 13.3% ± 3.3% (SD) in the long‐term group and 12.5% ± 6.6% (SD) in the short‐term group. Zidovudine triphosphate accounted for 13.4% ± 4.1% (SD) in the long‐term group and 13.5% ± 8.3% (SD) in the short‐term group. Mean peak concentrations for the active zidovudine triphosphate were 0.04 ± 0.02 (SD) pmol/10 6 cells in both groups. Comparison of the individual zidovudine phosphate concentrations and P‐glycoprotein expression revealed no significant difference in the two patient populations. Conclusions These data suggest that intracellular phosphorylation does not change over time and that zidovudine does not select for P‐glycoprotein expressing cells. Clinical Pharmacology & Therapeutics (1996) 60 , 168–176; doi: