Journal
ANTIMICROBIAL AGENTS AND CHEMOTHERAPY
Volume 54, Issue 11, Pages 4619-4625Publisher
AMER SOC MICROBIOLOGY
DOI: 10.1128/AAC.00712-10
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Funding
- National Institute of Allergy and Infectious Diseases [K23 AI076106]
- National Institute of Biomedical Imaging and Bioengineering [R01 EB005803]
- Swiss National Science Foundation (SNF) [324700-112655, 32430-124943, 326000-121314/1]
- Medecins Sans Frontieres
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Atazanavir inhibits UDP-glucuronyl-transferase-1A1 (UGT1A1), which metabolizes raltegravir, but the magnitude of steady-state inhibition and role of the UGT1A1 genotype are unknown. Sufficient inhibition could lead to reduced-dose and -cost raltegravir regimens. Nineteen healthy volunteers, age 24 to 51 years, took raltegravir 400 mg twice daily (arm A) and 400 mg plus atazanavir 400 mg once daily (arm B), separated by >= 3 days, in a crossover design. After 1 week on each regimen, raltegravir and raltegravir-glucuronide plasma and urine concentrations were measured by liquid chromatography-tandem mass spectrometry in multiple samples obtained over 12 h (arm A) or 24 h (arm B) and analyzed by noncompartmental methods. UGT1A1 promoter variants were detected with a commercially available kit and published primers. The primary outcome was the ratio of plasma raltegravir C-tau, or concentration at the end of the dosing interval, for arm B (24 h) versus arm A (12 h). The arm B-to-arm A geometric mean ratios (95% confidence interval, P value) for plasma raltegravir C-tau, area under the concentration-time curve from 0 to 12 h (AUC(0-12)), and raltegravir-glucuronide/ raltegravir AUC(0-12) were 0.38 (0.22 to 0.65, 0.001), 1.32 (0.62 to 2.81, 0.45), and 0.47 (0.38 to 0.59, <0.001), respectively. Nine volunteers were heterozygous and one was homozygous for a UGT1A1 reduction-of- function allele, but these were not associated with metabolite formation. Although atazanavir significantly reduced the formation of the glucuronide metabolite, its steady-state boosting of plasma raltegravir did not render the C-tau with a once-daily raltegravir dose of 400 mg similar to the C-tau with the standard twice-daily dose. UGT1A1 promoter variants did not significantly influence this interaction.
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