Limited-Sampling Strategies for Therapeutic Drug Monitoring of Moxifloxacin in Patients With Tuberculosis

Background: Moxifloxacin (MFX) is a potent drug for multidrug resistant tuberculosis(TB) treatment and is also useful if first-line agents are not tolerated. Therapeutic drug monitoring may help to prevent treatment failure. Obtaining a full concentration-time curve of MFX for therapeutic drug monitoring is not feasible in most settings. Developing a limited-sampling strategy based on population pharmacokinetics (PK) may help to overcome this problem. Methods: Steady-state plasma concentrations after the administration of 400 mg of MFX once daily were determined in 21 patients with TB, using a validated liquid chromatography-tandem mass spectrometry method. A one-compartment population model was generated and crossvalidated. Monte Carlo data simulation (n = 1000) was used to calculate limited-sampling strategies. The correlation between predicted MFX AUC(0-24h) (area under the concentration-time curve 0 to 24 hours) and observed AUC(0-24h) was investigated by Bland-Altman analysis. Finally, the predictive performance of the final model was tested prospectively using MFX profiles from patients with TB receiving 400, 600, or 800 mg once daily. Results: Median minimum inhibitory concentration of Mycobacterium tuberculosis isolates was 0.25 mg/L (interquartile range: 0.25-0.5 mg/L). The geometric mean AUC(0-24h) was 24.5 mg.h/L (range: 8.5-72.2 mg.h/L), which resulted in a geometric mean AUC(0-24h)/minimum inhibitory concentration ratio of 72 (range: 21-321). PK analysis, based on PK profiles of 400 mg of MFX once daily, resulted in a crossvalidated population PK model with the following parameters: apparent clearance (Cl) 18.5 +/- 8.6 L/h per 1.85 m(2), V-d 3.0 +/- 0.7 L/kg corrected lean body mass, K-a 1.15 +/- 1.16 h 21, and F was fixed at 1. After the Monte Carlo simulation, the best predicting strategy for MFX AUC(0-24h) for practical use was based on MFX concentrations 4 and 14 hours postdosing (r(2) = 0.90, prediction bias = -1.5%, and root mean square error = 15%). Conclusions: MFX AUC(0-24h) in patients with TB can be predicted with acceptable accuracy for clinical management, using limited sampling. AUC(0-24h) prediction based on 2 samples, 4 and 14 hours postdose, can be used to individualize treatment.