Real-time therapeutic drug monitoring of cefozopran in plasma using high-performance liquid chromatography with ultraviolet detection

Personalised beta-lactam therapy: basic principles and practical approach

Bacterial infections are potentially life-threatening diseases requiring effective antibiotic treatment right from the outset to achieve a favourable prognosis. Therapeutic success depends on the susceptibility of the bacterial pathogen, determined by the minimum inhibitory concentration (MIC), and the concentration of the antibiotic at the focus of infection, which is influenced by drug metabolism and pharmacokinetic (PK) factors. Beta-lactams are time-dependent antibiotics. Bacterial killing correlates with the duration of the drug concentration above the MIC of the pathogen. Critical illness is associated with major PK changes. This may lead to unexpected drug concentrations and unpredictable dose requirements differing significantly from standard dosages. Emerging dosing strategies are therefore based on PK/pharmacodynamic (PD) principles. Therapeutic drug monitoring (TDM) is increasingly playing a key role in antibiotic treatment optimisation in general and in beta-lactam therapy, in particular, notably in severely ill patients. Furthermore, evidence of the superiority of continuous beta-lactam infusions over shorter administration regimens is growing. Target drug concentrations have to be defined, considering MIC values especially in pathogens with limited susceptibility. For reliable TDM results, correct pre-analytical sample handling is indispensable. Personalised, TDM-guided therapy currently offers the most promising approach to assuring that beta-lactam treatment is effective, especially in critically ill patients.

Stability of cefozopran hydrochloride in aqueous solutions

The influence of pH on the stability of cefozopran hydrochloride (CZH) was investigated in the pH range of 0.44-13.00. Six degradation products were identified with a hybrid ESI-Q-TOF mass spectrometer. The degradation of CZH as a result of hydrolysis was a pseudo-first-order reaction. As general acid-base hydrolysis of CZH was not occurred in the solutions of hydrochloric acid, sodium hydroxide, acetate, borate and phosphate buffers, kobs = kpH because specific acid-base catalysis was observed. Specific acid-base catalysis of CZH consisted of the following reactions: hydrolysis of CZH catalyzed by hydrogen ions (kH+), hydrolysis of dications (k1H2O), monocations (k2H2O) and zwitter ions (k3H2O) and hydrolysis of zwitter ions (k1OH-) and monoanions (k2OH-) of CZH catalyzed by hydroxide ions. The total rate of the reaction was equal to the sum of partial reactions: [Formula: see text]. CZH similarly like other fourth generation cephalosporin was most stable at slightly acidic and neutral pH and less stable in alkaline pH. The cleavage of the β-lactam ring resulting from a nucleophilic attack on the carbonyl carbon in the β-lactam moiety is the preferred degradation pathway of β-lactam antibiotics in aqueous solutions.

Pharmacokinetics of cefozopran by single and multiple intravenous infusions in healthy Chinese volunteers

BACKGROUND AND OBJECTIVES

Cefozopran is a parenteral cephalosporin with a broad spectrum of activity against Gram-positive and Gram-negative bacteria. The objective of this study was to evaluate the pharmacokinetics of cefozopran after single- and multiple-dose intravenous administration in healthy subjects, to provide clinical guidance in its application.

METHODS

This was a single-center, open-label, randomized, two-phase study conducted in 12 subjects. In the single-dose phase, subjects were randomly assigned to receive single doses of 0.5, 1.0 and 2.0 g of injected cefozopran hydrochloride in a three-way crossover design with a 5-day washout period between administrations. In the multiple-dose phase, subjects received 2.0 g every 12 h for 4 days. Plasma and urine pharmacokinetic samples were assayed by a validated high-performance liquid chromatography-tandem mass spectrometry method. Pharmacokinetic parameters were calculated and analyzed statistically. Safety assessments were conducted throughout the study.

RESULTS

Twelve healthy volunteers (six males and six females) were enrolled and completed the study. Following a single 1-h intravenous infusion of 0.5, 1.0 or 2.0 g cefozopran, maximum plasma concentration (C max) and area under the plasma concentration-time curve from time zero to the time of the last measurable concentration (AUClast) increased in a dose-proportional manner. The mean half-life in plasma (t ½) was in the range of 1.20-2.80 h. Cefozopran was mainly excreted in its unchanged form, with no tendency for accumulation, via the kidney, and varied from 65.99 to 73.33 %. No appreciable accumulation of either drug occurred with multiple intravenous doses of cefozopran, and pharmacokinetic parameters for cefozopran were similar on days 1 and 4. No serious adverse events were reported. Adverse events were generally mild.

CONCLUSION

Cefozopran was safe and well tolerated in the volunteers and displayed linear increases in the C max and AUClast values.

[Personalized optimization of beta-lactam regimens based on studies of the pharmacokinetics-pharmacodynamics at the target sites]

Beta-lactam antibiotics are used for the treatment of various infections such as intra-abdominal infections and bacterial meningitis. Beta-lactams act at the infection site and their antibacterial effects relate to the exposure time during which the drug concentrations remain above the minimum inhibitory concentration for bacteria (T>MIC). The penetration into and exposure of beta-lactams at the target sites, such as the abdominal cavity and the cerebrospinal space, are therefore considered to be good indicators of their efficacies. However, earlier clinical research has focused primary on the drug concentrations in plasma. We therefore examined the pharmacokinetics-pharmacodynamics of beta-lactams at the target sites, and analyzed them using a population pharmacokinetic modeling and statistical technique called Monte Carlo simulation. This review summarizes our recent findings on carbapenem and cephem antibiotics in peritoneal and cerebrospinal fluids, and our new approaches to personalize and optimize beta-lactam dosing regimens based on their site-specific pharmacokinetic-pharmacodynamic profiles.

Determination of total cefozopran concentrations in human peritoneal fluid by HPLC with cefepime as an internal standard: Comparative pharmacokinetics in the fluid and plasma

A simple, rapid and precise HPLC method using ultrafiltration to remove protein was developed to determine total cefozopran concentrations in human peritoneal fluid in the same manner as in human plasma, irrespective of the amount of protein. The recovery of cefozopran after ultrafiltration in peritoneal fluid was higher than that in plasma, because the protein content in peritoneal fluid was lower than that in plasma. Furthermore, it was found that an internal standard with a similar protein-binding ratio to cefozopran could revise the cefozopran loss by ultrafiltration in plasma and peritoneal fluid samples irrespective of the amount of protein. Therefore, it was concluded that cefepime may be used as an internal standard. Cefozopran and cefepime were detected by measuring their ultraviolet absorbances at 235 nm. The calibration curve obtained for cefozopran in peritoneal fluid was linear from 0.2 to 200 microg/ml. The intraday and interday precisions were less than 5.77% (CV), and the accuracy was between 96.3% and 108% above 0.2 micro/ml. The lower limit of detection was 0.05 micro/ml in peritoneal fluid, which was the same as that in plasma. The assay has been applied to therapeutic drug monitoring of cefozopran in both plasma and peritoneal fluid and has contributed to peritoneal pharmacokinetic studies in patients.

Pharmacokinetic-pharmacodynamic target attainment analysis of cefozopran in Japanese adult patients

This study aimed to perform a pharmacokinetic-pharmacodynamic (PK-PD) target attainment analysis to create a dosing strategy for cefozopran in Japanese adult patients. A total of 145 plasma concentration samples from 32 adult patients were used for a population pharmacokinetic modeling and Monte Carlo simulation to assess the probability of attaining the PK-PD target (70% of the time above the minimum inhibitory concentration for the bacterium). The final population pharmacokinetic model was based on a two-compartment model, and creatinine clearance (Cl(cr)) and body weight (BW) were the most significant covariates: Cl(l/h) = 0.0263 x Cl(cr) + 1.49, V (c)(l) = 0.185 x BW(0.931), Q(l/h) = 4.55, V (p)(l) = 5.86, where Cl is the clearance, V (c) is the volume of distribution of the central compartment, Q is the intercompartmental clearance, and V (p) is the volume of distribution of the peripheral compartment. The Monte Carlo simulation demonstrated that 1 g q 12 h achieved a PK-PD target attainment probability of > or =85% against Escherichia coli, Klebsiella pneumoniae, and Streptococcus pneumoniae isolates. However, against Haemophilus influenzae and Pseudomonas aeruginosa isolates, 1 g q 8 h and (2 g, 1 g, 1 g) q 8 h were required to achieve a high probability, which value varied with the Cl(cr) and BW of the patient. These results provide a PK-PD-based strategy for tailoring cefozopran regimens in Japanese adult patients.