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Antimicrobial Agents and Chemotherapy, July 2009, p. 2918-2927, Vol. 53, No. 7
0066-4804/09/$08.00+0 doi:10.1128/AAC.01138-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.
Population Pharmacokinetics of Acyclovir in Children and Young People with Malignancy after Administration of Intravenous Acyclovir or Oral Valacyclovir
L. Zeng,1,2
C. E. Nath,2,3*
E. Y. L. Blair,1
P. J. Shaw,3,4
K. Stephen,3
J. W. Earl,2
J. C. Coakley,2 and
A. J. McLachlan1,5
Faculty of Pharmacy, University of Sydney, Sydney, NSW 2006, Australia,1 Departments of Biochemistry,2 Oncology, Children's Hospital at Westmead, Westmead, NSW 2145, Australia,3 Department of Paediatrics and Child Health, University of Sydney, Sydney, NSW 2006, Australia,4 Centre for Education and Research on Ageing, Concord Hospital, Concord, NSW 2139, Australia5
Received 25 August 2008/ Returned for modification 25 November 2008/ Accepted 22 April 2009
Acyclovir is effective in the prevention and treatment of herpes simplex virus (HSV) and varicella-zoster virus (VZV) infections. The aim of this study was to characterize the population pharmacokinetics of acyclovir observed following treatment with intravenous acyclovir and oral valacyclovir (valaciclovir) in young people with malignancy. Plasma acyclovir concentration-time data were collected from 43 patients (age range, 9 months to 20 years) who had been given multiple doses of acyclovir (5 mg/kg of body weight) and/or valacyclovir (10 mg/kg). Nonlinear mixed-effect modeling was employed to analyze acyclovir population pharmacokinetics and identify influential covariates. Simulations (n = 1,000) were conducted to explore the ability of the current doses to maintain acyclovir concentrations above the recommended 50% inhibitory concentration for HSV or VZV (0.56 mg/liter or 1.125 mg/liter, respectively) for more than 12 h. A one-compartment pharmacokinetic model with first-order elimination best described the acyclovir concentration-time data. The population mean estimates for clearance (CL), volume of distribution (V), absorption rate (ka), and bioavailability (F) were 3.55 liters/h, 7.36 liters, 0.63 h–1, and 0.60, respectively. Inclusion of body weight and estimated creatinine CL (CLCR) in the final model reduced the interindividual variabilities in CL and V from 61% to 24% and from 75% to 36%, respectively. Simulations revealed that with the use of the current doses, maximal efficacy can be achieved in over 45% of patients weighing 25 to 50 kg and with CLCR levels of 2.0 to 4.0 liters/h/m2, but only in a much smaller proportion of patients, with low weights (10 kg) and high CLCRs (5.5 liters/h/m2), suggesting that higher doses are required for this subgroup. This validated population pharmacokinetic model for acyclovir may be used to develop dosing guidelines for safe and effective antiviral therapy in young people with malignancy.
* Corresponding author. Mailing address: Department of Biochemistry, Children's Hospital at Westmead, Hawkesbury Rd., Locked Bag 4001, Westmead, NSW 2145, Australia. Phone: 61-2-98453287. Fax: 61-2-98453332. E-mail: christan{at}chw.edu.au
Published ahead of print on 4 May 2009.
Antimicrobial Agents and Chemotherapy, July 2009, p. 2918-2927, Vol. 53, No. 7
0066-4804/09/$08.00+0 doi:10.1128/AAC.01138-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.
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