Pharmacokinetics of cefotaxime and desacetylcefotaxime in elderly patients

Pharmacokinetics and Target Attainment of ß-lactam Antibiotics in Older People: A Systematic Review of Current Literature

BACKGROUND AND OBJECTIVE

(Patho)physiological changes in older people may influence the pharmacokinetics (PK), and consequently the target attainment, of ß-lactam antibiotics using standard dosing regimens. This systematic review compiles the current knowledge on the PK and target attainment of ß-lactam antibiotics in older people, with the aim to identify priorities for dose optimization in this patient population.

METHODS

A systematic literature search of the PubMed and EMBASE databases was conducted. Relevant articles published prior to 1 December 2021 were identified as eligible when they included data on the PK of ß-lactam antibiotics in adults ≥ 65 years of age. Extracted information included reported PK parameters (volume of distribution, clearance [CL], elimination rate constant, intercompartmental CL, elimination half-life, area under the concentration-time curve, maximum and trough concentration), covariates on PK parameters, target attainment rate, and dosing recommendations.

RESULTS

Ninety-one relevant articles were included in this review. Four main ß-lactam subclasses were represented: 59.3% on cephalosporins + cephamycins, 25.3% on penicillins, 15.4% on carbapenems, and 3.3% on monobactams; 65.9% of articles involved intravenous administration, 16.5% mixed administration routes, 12.1% oral administration, and 5.5% intramuscular administration. The majority of studies had a small sample size, often did not include detailed information on the study population and methods, and were fairly old. CL was, on average, decreased, while elimination half-life was prolonged in aged subjects compared with young subjects. Volume of distribution was generally similar between age groups. Most studies identified renal function as the most important contributor to altered drug CL. In only 30.8% of the articles, target attainment was studied, and in 35.7% of these articles, target attainment was found to be suboptimal. Dosing recommendations were incorporated in 87.9% of articles.

CONCLUSION

Studies frequently fail to provide an evidence-based dosing recommendation for this diverse patient population. Model-based PK studies that address both physiological and disease-related changes are urgently needed. This review identified gaps of knowledge to set priorities for further research.

Pharmacokinetic modelling of cefotaxime and desacetylcefotaxime--a population study in 25 elderly patients

OBJECTIVE

To develop a pharmacostatistical model to simultaneously characterise the pharmacokinetics of cefotaxime and its main metabolite, desacetylcefotaxime, in elderly patients.

METHODS

Cefotaxime, 1 g, was infused three times daily to 25 elderly patients, 66-93 years old. Cefotaxime and desacetylcefotaxime plasma concentrations (289 and 304 samples, respectively), along with demographic and physiological characteristics, were analysed using a population approach.

RESULTS

Cefotaxime pharmacokinetics was best described by a two-compartment open model in which desacetylcefotaxime was produced from the central compartment. The final parameter estimates were derived from simultaneous fit of parent/metabolite data. Cefotaxime clearance, mean 5.5 l/h, was positively influenced by body weight and serum protein concentration and negatively influenced by serum creatinine and age. In contrast, desacetylcefotaxime elimination was only decreased by age. The mean terminal half-lives of cefotaxime and desacetylcefotaxime were 1.7 h and 2.6 h, respectively. The stability and predictive performance of the final population pharmacokinetic model was assessed using 200 bootstrap samples of the original data.

CONCLUSION

Cefotaxime and desacetylcefotaxime elimination decreased with increasing age above 60 years. This decreased elimination was related to individual characteristics that are typically related to renal function.

Meropenem in elderly and renally impaired patients

The safety profile of meropenem in the elderly (aged > 65 years, n=843) and/or renally impaired (creatinine clearance < 51 ml/min, n=436) was assessed by evaluating data from 26 phase III studies which compared the use of meropenem (0.5 or 1.0 g, i.v. every 8 h) with other antimicrobial agents in patients with bacterial infections. The overall pattern and frequency of adverse events following meropenem therapy in the elderly and/or renally impaired were similar to those in younger and/or non-renally impaired cohorts and to imipenem/cilastatin and injectable third generation cephalosporins. Both dosages of meropenem (0.5 and 1.0 g, i.v. every 8 h) were generally well tolerated. There was no clinically significant mean change in indicators of renal flux between baseline and the end of treatment in any patient sub-group. Importantly, meropenem-related seizures were rare (0.1%), even in patients with renal impairment. In summary, meropenem has an excellent safety profile and is therefore suitable for use in elderly and/or renally impaired patients.

Pharmacokinetics of cefotaxime in healthy volunteers and patients

Cefotaxime is a third-generation cephalosporin that has maintained good susceptibility pattern despite its extensive use. It is available for intravenous and intramuscular administration. Its pharmacokinetic property includes a small volume of distribution with low protein binding. Cefotaxime's half-life is approximately 1.1 h, and it is primarily eliminated by the kidney. It has an active metabolite desacetyl-cefotaxime that displays pharmacokinetic properties similar to cefotaxime. Desacetyl-cefotaxime has a half-life of 1.5 h and also is eliminated by the kidneys by both glomerular filtration and active secretion. The half-life of cefotaxime and its metabolite is altered in patients with severe renal dysfunction requiring dosage adjustment. Despite its relatively short half-life, cefotaxime may be dosed every 12 h based on its pharmacokinetic and pharmacodynamic properties.

Pharmacodynamic (kinetic) considerations in the treatment of moderately severe infections with cefotaxime

Information about the pharmacodynamics of beta-lactams has accumulated rapidly over the last 20 years, and their application to cefotaxime are discussed in this review. Application of pharmacodynamics requires an integration of the pharmacokinetic and in vitro properties of the agent. Cefotaxime is similar to other beta-lactams in that it has little concentration-dependent killing and produces no postantibiotic effect against Gram-negative bacteria. However, it has a microbiologically active metabolite, deascetylcefotaxime, which can show synergy, partial synergy, or an additive effect in combination with the parent drug. More than any other technique, animal models have been able to elucidate the pharmacokinetic parameters that predict efficacy in vivo. They have shown that for beta-lactams it is the time that levels exceed the minimum inhibitory concentration (MIC) that is the most important determinant of efficacy. For bacteria to have no postantibiotic effect, plasma levels need to exceed the MIC for the whole of the dosing interval to achieve maximum killing at the site of infection. When applying these concepts as the most stringent criteria for efficacy using pharmacokinetic values from young, healthy volunteers, it can be shown that organisms with MICs of < or = 0.03 microgram/ml for a 1-g dose and 0.06 microgram/ml for a 2-g dose to achieve optimum efficacy with 12-h dosing of cefotaxime. However, two clinical studies have demonstrated trough levels much greater than would be predicted from these pharmacokinetic values, as a result of the effects of decreased renal function accompanying sepsis and older age. These studies showed that organisms with MICs < or = 1 microgram/ml for a 1-g dose or 2 micrograms/ml for a 2-g 12-h dose were covered for the whole of the dosing interval. Thus, all strains of Enterobacteriaceae and pathogenic Neisseria spp. that lack resistance mechanisms to third-generation cephalosporins would be covered using 12-h dosing schedules.

Retrospective analysis of the clinical and economic outcomes of twice-daily dosing of cefotaxime in a Canadian tertiary care institution

A retrospective analysis of the clinical and economic outcome of a regimen of cefotaxime 1 g given every 12 h was conducted following the introduction of an institutional policy recommending this new dosing strategy. Patients were identified from a log order entry in the pharmacy, and the medical records were reviewed using a standardized data collection form. Explicit criteria were applied for the indications for antimicrobial therapy, presence of infection, and outcome parameters. A total of 60 patients with a mean (+/- SD) age of 56.2 (+/- 17.8) years and a mean (+/- SD) length of stay of 20.75 (+/- 18.1) days were identified. Of these, 48 (80%) were found to have a clinically or microbiologically documented infection, and of the 42 patients who could be assessed accordingly to the criteria chosen, 37 (88%) had a favorable clinical response; 21 patients (35%) received cefotaxime alone. The costs for administration of cefotaxime have decreased by approximately 30% since the introduction of this new dosing regimen.

Pharmacokinetics and dose proportionality of cefmetazole in healthy young and elderly volunteers

The pharmacokinetics and dose proportionality of cefmetazole were studied in 24 healthy volunteers (12 young and 12 elderly). Each volunteer received single 0.5-, 1-, and 2-g doses of cefmetazole administered intravenously over 5 min according to a three-way crossover design. Serial plasma and urine samples were collected over a 24-h period following dosing and assayed for cefmetazole by a high-performance liquid chromatography method. Results of the dose proportionality portion of the study indicated that cefmetazole pharmacokinetics are linear and proportional with dose in both age groups. Comparisons of pharmacokinetic parameters between the young and elderly groups indicated that the systemic clearance was significantly lower in elderly than in young volunteers (92.4 versus 112 ml/min). Additionally, creatinine clearance was significantly lower in elderly (74.1 ml/min) than in young (92.9 ml/min) subjects. No significant differences between age groups were observed for volume of distribution, urinary recovery, terminal half-life, nonrenal clearance, or renal clearance, although half-life was slightly prolonged in elderly volunteers relative to that in young volunteers (1.54 versus 1.34 h), and renal clearance was slightly lower in elderly than in young volunteers (83.7 versus 96.1 ml/min). Both systemic and renal clearance were significantly correlated with creatinine clearance. These results indicate that the observed age-related differences in the pharmacokinetics of cefmetazole are most likely due to differences in renal function between the two age groups. The small reduction in cefmetazole elimination in the elderly would not warrant dose adjustment in this population.