Microdialysis combined with liquid chromatography-tandem mass spectrometry for the quantitation of gemifloxacin and its application to a muscle penetration study in healthy and MRSA-infected rats.

Rui Zhao,Xue-Fu You,Cong-Ran Li,Qing Wang,Jing Pang,Xin-Xin Hu,Xiukun Wang,Xi Lu,Xin-Yi Yang,Jian-Dong Jiang,Tong-Ying Nie,Hua Zhou

doi:10.1371/journal.pone.0217573

Rui Zhao, Xue-Fu You + Show 10 more

Open Access

https://doi.org/10.1371/journal.pone.0217573

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Abstract

Pharmacological efficacy is based on the drug concentration in target tissues, which usually cannot be represented by the plasma concentration. The purpose of this study was to compare the pharmacokinetic characteristics of gemifloxacin in plasma and skeletal muscle and evaluate its tissue penetration in both healthy and MRSA (methicillin-resistant Staphylococcus aureus)-infected rats. A microdialysis (MD) combined with liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated to determine free gemifloxacin concentrations in rat plasma and skeletal muscle simultaneously. The in vivo recoveries of MD were 23.21% ± 3.42% for skeletal muscle and 20.62% ± 3.19% for plasma, and were concentration independent. We provided evidence that the method developed here meets FDA requirements. Additionally, this method was successfully applied to the determination of free gemifloxacin in rats. Muscle and blood dialysates were collected after an 18 mg/kg intravenous bolus dose. The mean areas under the concentration-time curves (AUCs) from 0 to 9 h for skeletal muscle and plasma were 3641.50 ± 915.65 h*ng/mL and 7068.32 ± 1964.19 h*ng/mL in MRSA-infected rats and 3774.72 ± 700.36 h*ng/mL and 6927.49 ± 1714.86 h*ng/mL in healthy rats, respectively. There was no significant difference (P>0.05) in gemifloxacin exposure between healthy rats and MRSA-infected rats for plasma or muscle. The low ratio of AUC0-9 muscle to AUC0-9 plasma suggested lower drug exposure in skeletal muscle than in plasma for both healthy and MRSA-infected rats. Our study suggested that the administration of gemifloxacin according to drug levels in plasma to treat local infection is unreasonable and might result in an inadequate dose regimen.

Highlights

Antibacterial drug resistance, an urgent global crisis, is seriously threatening public health and social stability
Pharmacological efficacy is usually related to the free drug concentration in target tissues, but the plasma concentration obtained in pharmacokinetic (PK) studies does not represent the real concentration in the tissue, even taking the protein binding rate into consideration [6]
Selectivity was evaluated by comparing the chromatograms of blank dialysate, blank dialysate spiked with gemifloxacin (40 ng/mL), and dialysate of skeletal muscle or plasma collected 4 h postdose

Summary

Introduction

Antibacterial drug resistance, an urgent global crisis, is seriously threatening public health and social stability. The prevalence of methicillin-resistant Staphylococcus aureus (MRSA), a major cause of hospital and community-associated infections, has become the focus of novel antibacterial development. Gemifloxacin shows a better inhibitory effect on topoisomerase IV, a primary target of Staphylococcus aureus [2]. Pharmacological efficacy is usually related to the free drug concentration in target tissues, but the plasma concentration obtained in pharmacokinetic (PK) studies does not represent the real concentration in the tissue, even taking the protein binding rate into consideration [6]. Microdialysis (MD), a technique used to sample protein-free molecules located in a target site by a dialysis membrane, provides the possibility to achieve an appropriate drug concentration in target tissues and is widely utilized in the tissue distribution studies [7,8]

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