Garenoxacin pharmacokinetics in subjects with renal impairment

Garenoxacin pharmacokinetics in patients undergoing maintenance hemodialysis

INTRODUCTION

Studies on the pharmacokinetics of the antibiotic garenoxacin (GRNX) in patients with renal insufficiency are lacking. In this study, we attempted to ascertain the appropriate dose of GRNX in patients undergoing maintenance hemodialysis (MH) based on pharmacokinetic parameters and clinical outcomes.

METHODS

Six male patients with infections who were undergoing MH received 200 mg GRNX once daily. Blood samples were taken before and at 1, 2, 4, 6, 12, and 24 hours after GRNX administration. Plasma GRNX concentrations were measured using high-performance liquid chromatography.

FINDINGS

The mean maximum plasma concentration (C_max ) was 3.00 ± 1.12 µg/mL, time to maximum plasma concentration (T_max ) was 3.0 ± 2.0 hours, and area under the curve for 24 hours (AUC_0-24 ) was 40.7 ± 16.7 µg·h/mL. The half-life (T_1/2 ) of GRNX could not be calculated because plasma concentrations remained high 24 hours after administration. C_max was strongly associated with the GRNX dose per kilogram body weight (r = 0.85, P = 0.03). Clinically, fever resolved within 3 days of GRNX administration and C-reactive protein levels returned to normal 14 days after administration. One patient experienced temporary increases in serum transaminase levels.

DISCUSSION

MH patients receiving 200 mg GRNX once daily for infection showed a reduced C_max but similar AUC_0-24 compared with healthy individuals. While this study evaluated the effect of GRNX treatment, further research is needed to assess the accumulation of GRNX and the impact of continuous administration on its pharmacokinetics, as well as to prevent the development of resistant mutants.

Optimal dose finding of garenoxacin based on population pharmacokinetics/pharmacodynamics and Monte Carlo simulation

Purpose

Garenoxacin, a novel des-F(6)-quinolone, possesses potent antibacterial activity against infectious pathogens in the respiratory tract. Population pharmacokinetic/pharmacodynamic (PK/PD) modeling and Monte Carlo simulations were used to optimize garenoxacin dosage regimens.

Methods

At the end of phase II stage, the clinical dose of garenoxacin was predicted to be 400 mg once daily by the interim PK/PD analysis using phase I and phase II clinical data. The criteria used to determine an optimal dose were (1) the target attainment of the area under the unbound concentration–time curve divided by the minimum inhibitory concentration (fAUC₀₋₂₄/MIC ratio) and (2) the maintenance of a trough concentration above the mutant prevention concentration. In a confirmatory phase III study, garenoxacin was administered 400 mg once daily to 136 patients infected with mild or moderate chronic respiratory diseases.

Results

Logistic regression analysis showed that fAUC₀₋₂₄/MIC ratio was a significant variable that predicted clinical response (p = 0.0164). Of all subjects, 92.4% reached the target value of fAUC₀₋₂₄/MIC ratio > 30 h, and the clinical efficacy rate of this population was 91.8%. On the other hand, there was no significant relationship between exposure values (AUC₀₋₂₄ and maximum concentration) and the incidence of adverse events by the Mann–Whitney test.

Conclusions

The antimicrobial efficacy of the actual phase III study was consistent with the expectation from the Monte Carlo PD simulation. We were able to show that the optimal garenoxacin dosage regimens were successfully determined using prospective population PK/PD analysis and clinical trial simulations.

Electronic supplementary material

The online version of this article (doi:10.1007/s00228-011-1095-3) contains supplementary material, which is available to authorized users.