AIDSWEEKLY Plus; Monday, May 18, 2009
Staff Medical Writers

2009 MAY 18 - (NewsRx.com) -- "Abacavir (ABC) is administered either at 600 mg once daily (ABC 600 mg QD) or 300 mg twice daily (ABC 300 mg BID) in anti-human immunodeficiency virus (anti-HIV) combination therapy. Although ABC plasma pharmacokinetics following each regimen has been well defined, no study has directly compared the regimens with respect to pharmacokinetics of ABC's active intracellular anabolite, carbovir-triphosphate (CBV-TP)," scientists in the United States report (see also HIV/AIDS).

"In an open-label, two-period, crossover study, 34 HIV-infected male and female subjects stabilized on antiretroviral regimens containing either ABC 600 mg QD or ABC 300 mg BID received their usual doses on days -1 and 1 and then switched regimens for days 2 to 11. Serial blood samples collected on days 1 and 11 were assayed for plasma ABC and intracellular CBV-TP concentrations using validated high-performance liquid chromatography-tandem mass spectrometry methods. Pharmacokinetic parameters were calculated using noncompartmental methods. Analysis of variance with a mixed-effect model was performed for treatment and gender comparisons. In 27 evaluable subjects, the regimens provided bioequivalent ABC daily areas under the concentration-time curve from 0 to 24 h (AUC(0-24)) and comparable CBV-TP concentrations at the end of the dosing interval (C-tau). As expected, ABC QD resulted in 109% higher ABC maximum concentrations of drug in plasma (C-max) than did ABC BID. ABC QD also resulted in 32% higher CBV-TP AUC(0-24) and 99% higher CBV-TP C-max than did ABC BID. Females had a 38% higher weight-adjusted ABC AUC(0-24) and 81% higher weight-adjusted CBV-TP AUC(0-24) than did males. Virologic suppression was maintained during regimen switch, and no tolerability differences between regimens were observed," wrote G. Moyle and colleagues, GlaxoSmithKline.

The researchers concluded: "This study showed that ABC 600 mg QD and ABC 300 mg BID regimens led to similar intracellular CBV-TP C-tau values, thus providing pharmacokinetic support for the interchangeability of these two regimens. Women had higher intracellular CBV-TP exposure than did men."

Moyle and colleagues published their study in Antimicrobial Agents and Chemotherapy (Steady-State Pharmacokinetics of Abacavir in Plasma and Intracellular Carbovir Triphosphate following Administration of Abacavir at 600 Milligrams Once Daily and 300 Milligrams Twice Daily in Human Immunodeficiency Virus-Infected Subjects. Antimicrob Agents Chemother. 2009 Apr;53(4):1532-8.

For additional information, contact I.H. Song, GlaxoSmithKline Inc., 17-2229-2B, 5 Moore Dr., Research Triangle Pk, NC 27709, USA.

The publisher's contact information for the journal Antimicrobial Agents and Chemotherapy is: American Society Microbiology, 1752 N St. NW, Washington, DC 20036-2904, USA.

Keywords: United States, HIV/AIDS, AIDS, Abacavir, Acquired Immune Deficiency Syndrome, Acquired Immunodeficiency Syndrome, Anti-Infectives, Antimicrobials, Antivirals, Carbovir, Chemotherapy, Combination Therapy, Diagnosis, Diagnostics, Drug Therapy, Drugs, GlaxoSmithKline, HIV, Human Immunodeficiency Virus, Immunology, Liquid Chromatography, Mass Spectrometry, Nucleoside Reverse Transcriptase Inhibitor, Pharmaceutical Business, Pharmaceutical Company, Pharmaceuticals, Pharmacokinetics, Sexually Transmitted Disease, Therapies, Treatment, Viral, Virology, GlaxoSmithKline.

This article was prepared by AIDS Weekly editors from staff and other reports.

2009-05-18
AW090508

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