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Antimicrobial Agents and Chemotherapy, May 1998, p. 1098-1104, Vol. 42, No. 5
Division of Clinical Pharmacology,
Received 8 July 1997/Returned for modification 31 December
1997/Accepted 10 February 1998
Population pharmacokinetic modeling is a useful approach to
obtaining estimates of both population and individual pharmacokinetic parameter values. The potential for relating pharmacokinetic parameters to pharmacodynamic outcome variables, such as efficacy and toxicity, exists. A logistic regression relationship between the probability of a
successful clinical and microbiological outcome and the peak concentration-to-MIC ratio (and also the area under the plasma concentration-time curve [AUC]/MIC ratio) has previously been developed for levofloxacin; however, levofloxacin assays for
determination of the concentration in plasma are not readily available.
We attempted to derive and validate demographic variable models to
allow prediction of the peak concentration in plasma and clearance (CL)
from plasma for levofloxacin. Two hundred seventy-two patients received
levofloxacin intravenously for the treatment of community-acquired
infection of the respiratory tract, skin or soft tissue, or urinary
tract, and concentrations in plasma, guided by optimal sampling theory, were obtained. Patient data were analyzed by the Non-Parametric Expectation Maximization approach. Maximum a posteriori
probability Bayesian estimation was used to generate individual
parameter values, including CL. Peak concentrations were simulated from these estimates. The first 172 patients were used to produce
demographic models for the prediction of CL and the peak concentration.
The remaining 100 patients served as the validation group for the model. A median bias and median precision were calculated. A
two-compartment model was used for the population pharmacokinetic
analysis. The mean CL and the mean volume of distribution of the
central compartment (V1) were 9.27 liters/h and
0.836 liter/kg, respectively. The mean values for the
intercompartmental rate constants, the rate constant from the central
compartment to the peripheral compartment (Kcp)
and the rate constant from the peripheral compartment to the central
compartment (Kpc), were 0.487 and 0.647 h
0066-4804/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Levofloxacin Population Pharmacokinetics and Creation of a
Demographic Model for Prediction of Individual Drug Clearance in
Patients with Serious Community-Acquired Infection
1, respectively. The mean peak concentration and the
mean AUC values normalized to a dosage of 500 mg every 24 h were
8.67 µg/ml and 72.53 µg · h/ml, respectively. The variables
included in the final model for the prediction of CL were creatinine
clearance (CLCR), race, and age. The median bias and median
precision were 0.5 and 18.3%, respectively. Peak concentrations were
predicted by using the demographic model-predicted parameters of CL,
V1, Kcp, and Kpc, in the simulation. The median bias and the
median precision were 3.3 and 21.8%, respectively. A population model
of the disposition of levofloxacin has been developed. Population
demographic models for the prediction of peak concentration and CL from
plasma have also been successfully developed. However, the
performance of the model for the prediction of peak concentration was
likely insufficient to be of adequate clinical utility. The model for the prediction of CL was relatively robust, with acceptable bias and
precision, and explained a reasonable amount of the variance in the CL
of levofloxacin from plasma in the population
(r2 = 0.396). Estimated CLCR, age,
and race were the final model covariates, with CLCR
explaining most of the population variance in the CL of levofloxacin
from plasma. This model can potentially optimize the benefit derived
from the pharmacodynamic relationships previously developed for
levofloxacin.
*
Corresponding author. Mailing address: Division
of Clinical Pharmacology, Departments of Medicine and Pharmacology
A-142, Albany Medical College, 47 New Scotland Ave., Albany, NY 12208. Phone: (518) 262-6330. Fax: (518) 263-6333. E-mail:
GLDRUSANO{at}AOL.COM.
Antimicrobial Agents and Chemotherapy, May 1998, p. 1098-1104, Vol. 42, No. 5
0066-4804/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
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