Cefepime distribution by microdialysis in peritoneal fluid of rats with or without experimental peritonitis.

The aim of this study was to investigate the penetration of cefepime into rat peritoneal fluid by microdialysis and to determine the relationship between unbound drug plasma and tissue concentration in healthy animals and in a sepsis model established through cecal ligation and puncture-induced peritonitis. Probe recovery was performed by dialysis and retrodialysis. Cefepime was administered at a dose of 110 mg/kg intravenously. Samples were collected for about 4 h, and concentrations were determined by liquid chromatography-electrospray ionization-QTOF MS. Tissue penetration was also determined. Probe recovery in vivo was 38.78% ± 3.31% and 38.83% ± 2.74% in the control and peritonitis groups, respectively. Cefepime was rapidly distributed in the peritoneal fluid in both groups. The peritoneal fluid/plasma cefepime ratio was 0.38 and 0.32 for the control and peritonitis groups, respectively. Cefepime concentrations were above the MIC of 4 mg/L for the main enterobacteria. The infection model that was used had no apparent effect on the pharmacokinetics of cefepime in rats. This was the first study to determine free cefepime concentrations in the peritoneal fluid of healthy rats and rats with experimental peritonitis.

Fast determination of free metronidazole in rat plasma and peritoneal fluid using HPLC-UV method.

Peritonitis refers to the inflammatory reaction of the peritoneum to aggression. In addition, it contributes significantly to sepsis. The presence of free concentrations of antimicrobials above the minimum inhibitory concentration at the site of infection is critical to therapeutic response. Metronidazole (MTZ) is an antimicrobial used to treat peritonitis because of its effectiveness against anaerobic microorganisms. This study investigates free MTZ concentrations in peritoneal microdialysate in Wistar rats. A C18 column (150 × 4.0 mm, 5 µm) was used for the analysis conducted at 40°C under isocratic conditions. The mobile phase consisted of acetonitrile and an aqueous solution of 50-mM monobasic phosphate buffer and 0.1% triethylamine, with pH 3.0 (10:90, v/v). MTZ calibration was linear in the range of 0.5-30.0 µg/ml. The intra- and inter-day precision was satisfactory with relative standard deviation ≤5.67%. The accuracy ranged from 90.64 to 103.77%, and the lower limit of quantification was 0.5 µg/ml. The developed method was successfully applied in a pilot pharmacokinetic study after MTZ administration (30 mg/kg, intravenously) in rats. The main advantage of the employed method is that it does not require sample processing and protein removal steps. This is the first study to be conducted using MTZ in rats.

Development and validation of an LC-ESI-QTOF-MS method to measure cefepime in the plasma and peritoneal fluid of rats using microdialysis: Application in a pilot pharmacokinetic study.

Cefepime (CEF) is a cephalosporin and can be administered in secondary peritonitis together with metronidazole to treat sepsis. This study aimed to develop and validate an LC-ESI-QTOF-MS method for the quantification of cefepime in the plasma and peritoneal microdialysate of healthy Wistar rats. Chromatographic separation was performed using a CLC-ODS C18 column (250 × 4.6 mm), a C18 pre-column (4 mm, 5 µm) and isocratic elution. Gallic acid was used as the internal standard. The mobile phase consisted of (A) ultrapure water (pH adjusted to 3.5) and (B) acetonitrile (80:20, v/v) at 0.8 ml/min. Quantification was performed using a mass spectrometer with electrospray ionization in positive mode to monitor ions with m/z 481.1322 (CEF) and m/z 171.0288 (IS). The method was validated for selectivity, precision, accuracy, linearity, stability, lower limit of quantification, carryover, recovery and matrix effect. Calibration was done in the ranges 1-40 and 1-100 µg/ml for the peritoneal microdialysate and plasma, respectively. Plasma extraction recovery ranged from 93.9 to 99.9%. The technique was validated and successfully applied in a pilot pharmacokinetic study for estimating the free concentration of CEF in the peritoneal microdialysate of rats for the first time.