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Antimicrobial Agents and Chemotherapy, May 2007, p. 1822-1826, Vol. 51, No. 5
0066-4804/07/$08.00+0     doi:10.1128/AAC.00570-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Compartmental Pharmacokinetic Analysis of Oral Amprenavir with Secondary Peaks{triangledown}

Olanrewaju Okusanya,1 Alan Forrest,1 Robin DiFrancesco,1 Sanela Bilic,1 Susan Rosenkranz,2 Michael F. Para,3 Elizabeth Adams,4 Kevin E. Yarasheski,5 Richard C. Reichman,6 Gene D. Morse,1* and the ACTG 5043 Protocol Team {dagger}

University at Buffalo School of Pharmacy, SUNY, Buffalo, New York,1 Harvard University, Boston, Massachusetts,2 Ohio State University, Columbus, Ohio,3 NIAID, Division of AIDS, Bethesda, Maryland,4 Washington University, St. Louis, Missouri,5 University of Rochester, Rochester, New York6

Received 9 May 2006/ Returned for modification 7 July 2006/ Accepted 25 January 2007

Amprenavir is a protease inhibitor that has been shown to have secondary peaks postulated to be due to enterohepatic recycling. We propose a model to describe the pharmacokinetics of amprenavir which accommodates the secondary peak(s). A total of 82 healthy human immunodeficiency virus (HIV)-seronegative subjects were administered a single 600-mg dose of amprenavir as part of adult AIDS Clinical Trials Group protocol A5043. Serial blood samples were obtained over 24 h. Samples were analyzed for amprenavir and fit to a compartmental model using ADAPT II software, with all relevant parameters conditional with respect to bioavailability. The model accommodated secondary peaks by incorporating clearance out of the central compartment with delayed instantaneous release back into the gut compartment. The data were weighted by the inverse of the estimated measurement error variance; model discrimination was determined using Akaike's Information Criteria. A total of 76 subjects were evaluable in the study analysis. The data were best fit by a two-compartment model, with 98.7% of the subjects demonstrating a secondary peak. Amprenavir had a mean total clearance of 1.163 liters/h/kg of body weight (0.7), a central volume of distribution of 1.208 liters/kg (0.8), a peripheral volume of distribution of 8.2 liters/kg (0.81), and distributional clearance of 0.04 liters/h/kg (0.81). The time to the secondary peak was 7.86 h (0.17), and clearance into a recycling compartment was 0.111 liters/kg/h (0.74). Amprenavir pharmacokinetics has been well described using a two-compartment model with clearance to a recycling compartment and release back into the gut. The nature of the secondary peaks may be an important consideration for the interpretation of amprenavir plasma concentrations during therapeutic drug monitoring.

* Corresponding author. Mailing address: Department of Pharmacy Practice, School of Pharmacy and Pharmaceutical Sciences, University at Buffalo, 317 Hochstetter Hall, Amherst, NY 14260. Phone: (716) 645-2828, ext. 252. Fax: (716) 645-2886. E-mail: emorse{at}buffalo.edu

{triangledown} Published ahead of print on 5 February 2007.

{dagger} Members of the adult AIDS Clinical Trials Group and the ACTG 5043 Protocol Team are listed in Acknowledgments.

Antimicrobial Agents and Chemotherapy, May 2007, p. 1822-1826, Vol. 51, No. 5
0066-4804/07/$08.00+0     doi:10.1128/AAC.00570-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.





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