Microbiology, pharmacology, and clinical use of mezlocillin sodium

Population pharmacokinetics and dosing optimization of mezlocillin in neonates and young infants

OBJECTIVES

Mezlocillin is used in the treatment of neonatal infectious diseases. However, due to the absence of population pharmacokinetic studies in neonates and young infants, dosing regimens differ considerably in clinical practice. Hence, this study aimed to describe the pharmacokinetic characteristics of mezlocillin in neonates and young infants, and propose the optimal dosing regimen based on the population pharmacokinetic model of mezlocillin.

METHODS

A prospective, open-label pharmacokinetic study of mezlocillin was carried out in newborns. Blood samples were collected using an opportunistic sampling method. HPLC was used to measure the plasma drug concentrations. A population pharmacokinetic model was developed using NONMEM software.

RESULTS

Ninety-five blood samples from 48 neonates and young infants were included. The ranges of postmenstrual age and birth weight were 29-40 weeks and 1200-4000 g, respectively, including term and preterm infants. A two-compartment model with first-order elimination was developed to describe the population pharmacokinetics of mezlocillin. Postmenstrual age, current weight and serum creatinine concentration were the most important covariates. Monte Carlo simulation results indicated that the current dose of 50 mg/kg q12h resulted in 89.2% of patients achieving the therapeutic target, when the MIC of 4 mg/L was used as the breakpoint. When increasing the dosing frequency to q8h, a dose of 20 mg/kg resulted in 74.3% of patients achieving the therapeutic target.

CONCLUSIONS

A population pharmacokinetic model of mezlocillin in neonates and young infants was established. Optimal dosing regimens based on this model were provided for use in neonatal infections.

Development and Validation of a UPLC-MS/MS Method for Ultra-Trace Level Determination of Acyl Chloride Potential Genotoxic Impurity in Mezlocillin

3-Chlorocarbonyl-1-methanesulfonyl-2-imidazolidinone (CMI) is a critical intermediate used in the synthesis of mezlocillin drug substance and also a potential genotoxic impurity with acyl chloride moiety. The content of CMI in mezlocillin should be <0.16 ppm to avoid the carcinogenicity and mutagenicity threats to patients. Therefore, a workable determination of CMI was critically crucial for ensuring the safety of mezlocillin drug products. However, the conventional HPLC method is insufficient for detection limits at ppm or lower levels. Besides, the high activity of acyl chloride also raises a challenge to the direct measurement of CMI. Thus, we explored a simple esterification approach, which converts CMI into methyl 3-(methylonyl)-2-oxoimidazolidine-1-carboxylate completely by optimizing the reaction temperature and time. Furthermore, the selected reaction monitoring model of triple quadrupole mass spectrometer optimized by the Box-Behnken design significantly enhanced the sensitivity of ultra-trace level determination. The limit of detection and limit of quantification of the method were reached 0.014 and 0.02 ppm, respectively, in the following validation study. A sensitive and specific ultra-performance liquid chromatography tandem mass spectrometry method for ultra-trace level determination of acyl chloride potential genotoxic impurity in mezlocillin drug substance has been successfully established in this study, which will provide a practical quality control tool of mezlocillin.

A Validated LC-MS/MS Method for the Determination of Mezlocillin in Plasma: An Adapted Method for Therapeutic Drug Monitoring in Children

Background:

Mezlocillin is off-label used for the treatment of respiratory infections in children. Therapeutic Drug Monitoring (TDM) data are also limited in children. A sensitive Liquid chromatography- tandem mass spectrometry (LC–MS/MS) method adapted to children was developed and validated for the determination of mezlocillin plasma concentration in the present study.

Methods:

Mezlocillin, extracted from a volume of 50 μL plasma using acetonitrile, was analyzed on an online LC-MS/MS system with an Agilent 1290 Infinity UHPLC (Agilent Technologies, CA, USA) coupled to an AB SCIEX QTRAP 6500PLUS MS/MS (AB Sciex, Framingham, MA, USA) with ceftiofur as an internal standard. HPLC separation was performed on a C18 column with ultra-pure water and acetonitrile as gradient elution at a flow rate of 0.4 mL/min at 30°C. Analyst TM Version 1.5.2 (Applied Biosystems) was used for data acquisition. The total chromatographic run time was 1.6 min.

Results:

LC/MS/MS method used for TDM of mezlocillin in children was developed and validated. This assay has a lower limit of quantification of 0.025 μg/mL for mezlocillin with 50 μL plasma. Good linearity was achieved for mezlocillin over the range from 0.025 to 20 μg /mL. The acceptance criteria were met in all cases. Among 36 patients aged between 0.16-1.63 years old, only one patient had detectable trough concentration higher than 1 μg/mL.

Conclusion:

LC-MS/MS method with 50 μL plasma developed in this study was successfully applied to TDM of mezlocillin in children. The high variability of trough concentration highlighted that TDM is important to optimize mezlocillin therapy in children.

Comparative pharmacokinetics of two multiple-dose mezlocillin regimens in normal volunteers

Mezlocillin was previously reported to exhibit dose-dependent pharmacokinetics. These reports suggest that it may be possible to administer a relatively large dose at a longer interval than is usual and still achieve therapeutic concentrations in serum. In a randomized, crossover study, we compared concentrations of mezlocillin in serum after a single dose and at steady state in 12 healthy volunteers who received 4 g every 6 h and 5 g every 8 h. A slight, but statistically significant, dose-dependent effect was observed upon the area under the concentration-time curve and total body clearance. No accumulation was observed with either schedule. Although concentrations in serum were higher after the 5-g dose, the more frequent administration of the 4-g dose schedule produced serum concentrations above the MIC for susceptible bacteria for a greater portion of the day. In the absence of clear guidelines from human studies which relate serum concentrations to clinical response, the available data indicate that the more frequent dosage schedule is appropriate for severe infections.

The pharmacokinetics of antibiotics used to treat peritoneal dialysis-associated peritonitis

Antibiotics continue to be used frequently to treat CAPD-associated peritonitis. Selection of appropriate antibiotic doses and routes of administration has been based largely upon clinical experience. Early pharmacokinetic studies utilized patients being treated with IPD. The relevance of these studies to CAPD remains unknown. Little information exists on the effects of peritonitis on peritoneal drug transport. Until the effects of peritonitis during CAPD are better understood, pharmacokinetic data will be of limited value in designing specific treatment recommendations for this common complication of peritoneal dialysis.