Important note: Information in this article was accurate in December 2004. The state of the art may have changed since the publication date.
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AIDSWEEKLY Plus; Monday, December 27, 2004
Staff Medical Writers
"Cost and inconvenience limit the application of full 12-hour pharmacokinetic (PK) analysis for routine therapeutic drug monitoring of antiretroviral medications. We explore whether lopinavir (LPV) and ritonavir (RTV) exposures can be estimated with limited sampling for patients taking twice-daily LPV/RTV," investigators in Canada report.
"One hundred and one PK profiles from 81 patients, most receiving salvage therapies including twice-daily LPV/RTV, were obtained for the analysis. After a minimum of 2 weeks on a stable regimen, blood was drawn immediately before and at 1, 2, 4, 6, 8, 10, and 12 hours after a timed medication dose.
"Plasma drug concentrations were determined by a validated HPLC-MS-MS assay. Peak concentrations, evening troughs, and AUC(0-12hours) were entered into linear and log10-log10 linear regression models to determine the best correlation with LPV and RTV plasma concentrations using a maximum of 2 time points," wrote C.S. Alexander and coworkers.
"The accuracy and precision of PK parameter estimates of the resultant models were tested on data collected for an additional 25 patients. Twelve models using various combinations of 2 timed LPV concentrations afforded accurate (maximum % bias = -6.45) and precise (relative standard deviation <15%) estimates for the LPV peak concentration or AUC(0-12hours).
"Four sets of 2 concentrations provided simultaneous estimates of both PK parameters, researchers said, "with the best estimates derived from data collected at 2 and 6 hours postdose."
"Evening trough concentrations were the best estimators of the daily nadir; however," the author concluded, "no adequate substitute for collecting blood 12 hours postdose emerged from this analysis."
Alexander and colleagues published their study in Therapeutic Drug Monitoring (Simplification of therapeutic drug monitoring for twice-daily regimens of lopinavir/ritonavir for HIV infection. Ther Drug Monit. 2004 Oct;26(5):516-23.
For additional information, contact C.S. Alexander, St. Pauls Hospital, BC Center Excellence HIV AIDS, 613-1081 Burrard St., Vancouver, BC V6Z 1Y6, Canada.
The publisher of the journal Therapeutic Drug Monitoring can be contacted at: Lippincott Williams & Wilkins, 530 Walnut St., Philadelphia, PA 19106-3621, USA.
The information in this article comes under the major subject areas of HIV/AIDS, Antiretroviral Therapy and Therapeutic Drug Monitoring.
This article was prepared by AIDS Weekly editors from staff and other reports.
Reference
Alexander CS, Montaner JS, Asselin JJ, et al., "Simplification of therapeutic drug monitoring for twice-daily regimens of lopinavir/ritonavir for HIV infection", Ther Drug Monit. 2004 Oct;26(5):516-23.
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