Binding of temocillin to plasma proteins in vitro and in vivo: the importance of plasma protein levels in different populations and of co-medications

Population pharmacokinetics and dosing simulations of temocillin in liver-transplanted paediatric patients: a prospective, open-label, non-randomized study

OBJECTIVES

Temocillin is a β-lactam antibiotic used for preventing or treating bacterial infections in liver-transplanted children. We characterized its pharmacokinetics in plasma and ascitic fluid and proposed dosing regimens that maximize the achievement of effective drug exposures in this patient group.

METHODS

Patients aged 6-36 months received 25 mg/kg/12 h (n = 14) or 25 mg/kg/8 h (n = 23). Total and unbound temocillin concentrations were measured in plasma and ascitic fluid. Drug safety was monitored. Non-compartmental and population pharmacokinetic analyses were performed, together with Monte Carlo simulations.

RESULTS

No safety concerns were reported. For 25 mg/kg/12 h, the unbound mean (±standard deviation) Cmax and Cmin were 38 ± 16 and 2 ± 1 mg/L, respectively. For the 25 mg/kg/8 h dose, the unbound Cmax remained similar although the mean Cmin increased to 5 ± 3 mg/L. Protein binding was saturable. Median penetration in ascitic fluid from plasma was 82% (min-max: 63-95%). A three-compartment model with first-order elimination best described unbound pharmacokinetic profiles in plasma and ascitic fluid, with body weight and estimated glomerular filtration rate (GFR) as significant covariates. Monte Carlo simulations suggested that 90% probability of target attainment was achieved in both fluids with 25 mg/kg/12 h for MICs ≤4 mg/L, estimated GFR ≤180 mL/min/1.73 m2 or weight ≥6 kg, and with 25 mg/kg/8 h, for MICs ≤8 mg/L, GFR ≤120 mL/min/1.73 m2 or weight ≥11 kg.

DISCUSSION

Although adequate in many instances, the current dosing regimen is likely inadequate for patients with low body weight, high renal function, or bacteria with high MIC, emphasizing the need for patient-specific factors to be considered in dose selection. These data support the importance of paediatric pharmacokinetic studies to optimize drug dosing regimens.

Variable temocillin protein binding and pharmacokinetics in different clinical conditions: Implications for target attainment

AIMS

The beta-lactam antibiotic temocillin is increasingly used to treat extended-spectrum beta-lactamase (ESBL-producing) strains; however, its protein binding is complex. This study aims to predict unbound temocillin concentrations in various participant groups to determine its impact on the probability of target attainment (PTA) and to improve dosing recommendations.

METHODS

The plasma pharmacokinetics were analysed using non-linear mixed-effects modelling. Data from individuals in four groups: healthy volunteers (HV), urinary tract infection patients (UTI), ventriculitis patients and sepsis-ICU patients were included. Simulations were performed to compare the PTA for different dosing regimens and participant-groups.

RESULTS

A two-compartment protein-binding model best fitted the 1085 concentrations (543 unbound, 542 total). Temocillin clearance was influenced by creatinine clearance, serum albumin (ALB) and C-reactive protein (CRP). For 2 g q8h intermittent infusion, the PTAs at an MIC of 16 mg/L were 2.3%, 39.5%, 10.0% and 72.5%, for HV, UTI, ventriculitis and sepsis-ICU patients, respectively. The effects of the covariates on the PTA were simulated for two example patients with intermittent infusion: the PTAs at an MIC of 8 mg/L for a sepsis-ICU patient (CRP 300 mg/L, albumin 15 g/L) and a mild-UTI patient (CRP 30 mg/L, albumin 35 g/L) were 94.3% and 62.4%, respectively. Continuous infusion consistently outperformed intermittent infusion in achieving the desired pharmacodynamic target (time above MIC).

CONCLUSIONS

Our study underscores the significant variation in temocillin clearance and unbound fractions among different participant groups, challenging the efficacy of traditional 2 g q12h dosing. For patients with enhanced renal function and lower inflammation, continuous infusion emerges as a more effective strategy to achieve optimal target attainment.

The relation between inflammatory biomarkers and drug pharmacokinetics in the critically ill patients: a scoping review

BACKGROUND

The level of inflammation alters drug pharmacokinetics (PK) in critically ill patients. This might compromise treatment efficacy. Understanding the specific effects of inflammation, measured by biomarkers, on drug absorption, distribution, metabolism, and excretion is might help in optimizing dosing strategies.

OBJECTIVES

This review investigates the relationship between inflammatory biomarkers and PK parameters absorption, distribution, metabolism and excretion (ADME) in critically ill patients, providing insight in the complexity of dosing drugs in critically ill patients.

METHOD

Following PRISMA guidelines, we conducted a comprehensive search of Medline, Embase, Web of Science, and Cochrane databases (January 1946-November 2023). Studies examining inflammatory biomarkers, PK parameters, or drug exposure in critically ill patients were included. Records were screened by title, abstract, and full text, with any discrepancies resolved through discussion or consultation with a third reviewer.

RESULTS

Of the 4479 records screened, 31 met our inclusion criteria: 2 on absorption, 7 on distribution, 17 on metabolism, and 6 on excretion. In general, results are only available for a limited number of drugs, and most studies are done only looking at one of the components of ADME. Higher levels of inflammatory biomarkers may increase or decrease drug absorption depending on whether the drug undergoes hepatic first-pass elimination. For drug distribution, inflammation is negatively correlated with drug protein binding capacity, positively correlated with cerebrospinal fluid penetration, and negatively correlated with peritoneal penetration. Metabolizing capacity of most drugs was inversely correlated with inflammatory biomarkers. Regarding excretion, inflammation can lead to reduced drug clearance, except in the neonatal population.

CONCLUSION

Inflammatory biomarkers can offer valuable information regarding altered PK in critically ill patients. Our findings emphasize the need to consider inflammation-driven PK variability when individualizing drug therapy in this setting, at the same time research is limited to certain drugs and needs further research, also including pharmacodynamics.

Pharmacokinetic/pharmacodynamic model-based optimization of temocillin dosing strategies for the treatment of systemic infections

BACKGROUND

Temocillin is increasingly considered as an alternative to carbapenems. However, there is no consensus on optimal dosing strategies and limited data on temocillin efficacy in systemic infections.

OBJECTIVES

We compared temocillin dosing strategies using pharmacokinetic/pharmacodynamic (PK/PD) modelling and simulation based on plasma exposure and in vitro time-kill data.

METHODS

Temocillin effects on four Escherichia coli strains were evaluated using static time-kill experiments and the hollow-fibre infection model, in which unbound plasma concentrations following intermittent and continuous infusion regimens of 4 and 6 g daily were replicated over 72 h. A PK/PD model was developed to describe the time-kill data. The PK/PD model was coupled to a population PK model of temocillin in critically ill patients to predict bacterial killing and resistance development following various dosing regimens.

RESULTS

Amplification of resistant subpopulations was observed within 24 h for all strains. The PK/PD model described the observed bacterial kill kinetics and resistance development from both experimental systems well. Simulations indicated dose-dependent bacterial killing within and beyond the currently used daily dose range, and a superiority of continuous compared with intermittent infusions. However, regrowth of resistant subpopulations was frequently observed. For two strains, bacteriostasis over 72 h was predicted only with doses that are higher than those currently licensed.

CONCLUSIONS

Continuous infusions and 6 g daily doses of temocillin kill E. coli more effectively than 4 g daily doses and intermittent infusions, and may increase efficacy in the treatment of systemic infections. However, higher daily doses may be required to suppress resistance development.

Pharmacokinetics and pharmacological target attainment of standard temocillin dosing in non-critically ill patients with complicated urinary tract infections

OBJECTIVES

Temocillin, a carbapenem-sparing β-lactam antibiotic, is commonly used at the standard 4 g/day dosage for treating complicated urinary tract infections (cUTIs). However, pharmacokinetic/pharmacodynamic (PK/PD) data supporting this regimen is limited. This study evaluated the plasma pharmacokinetics (PK) and PTA of temocillin in non-critically ill cUTI patients with varying degrees of renal insufficiency (RI).

METHODS

In this single-centre clinical study, 22 cUTI patients received a fixed 4 g/day (2 g q12h, intravenously) temocillin dose, irrespective of renal function (no RI: n = 5, mild RI: n = 8, moderate RI: n = 9). Plasma samples were collected post-dosing for LC-MS analysis of total and unbound temocillin levels. Monte Carlo simulations were performed based on the established PK/PD target of ≥35% fT > MIC (minimal inhibitory concentration).

RESULTS

Among patients, the highest plasma drug exposure and PK/PD target attainment were observed in those with moderate RI (median AUC0-12h = 1143 h.mg/L and %fT > MIC = 68%), followed by mild RI patients (median AUC0-12h = 918 h.mg/L and %fT > MIC = 34%), and the lowest in those with healthy kidney function (median AUC0-12h = 692 h.mg/L and %fT > MIC = 26%). Simulations indicated that the 4 g/day temocillin dose achieves 90% PTA only for glomerular filtration rate < 60 mL/min and MIC ≤ 8 mg/L.

CONCLUSION

The standard temocillin dose may need to be increased from 4 to 6 g/day to treat non-critically ill cUTI patients, in line with recent EUCAST recommendations. For patients with moderate RI, who experience higher exposure due to reduced renal drug clearance, 4 g/day temocillin remains appropriate.

Population pharmacokinetics and dosing simulations of total and unbound temocillin in the plasma and CSF of neurocritically ill patients with external ventricular drain-related cerebral ventriculitis

BACKGROUND

Cerebral ventriculitis might be caused by Gram-negative bacteria, including ESBL producers. Temocillin may be a useful treatment option in this scenario; however, no consistent data are available regarding its penetration into the CSF.

OBJECTIVES

To describe the population pharmacokinetics of temocillin in plasma and CSF and to determine the probability for different simulated dosing regimens to achieve pharmacokinetic/pharmacodynamic (PK/PD) targets in the CSF.

METHODS

Ten post-neurosurgical critically ill adult patients requiring continuous drainage of CSF were included in this monocentric, prospective, open-label, non-randomized study. They received 2 g loading dose temocillin over 30 min IV infusion, followed by a 6 g continuous infusion over 24 h. Total and unbound concentrations were measured in plasma (n = 88 and 86) and CSF (n = 88 and 88) samples and used to build a population PK model. Monte Carlo simulations were performed to estimate the PTA at 100% Css>MIC (steady state concentration above the MIC) in CSF.

RESULTS

All patients were infected with Enterobacterales with temocillin MICs ≤8 mg/L. The median (min-max) temocillin penetration in CSF was 12.1% (4.3-25.5) at steady state. Temocillin unbound plasma pharmacokinetics were best described by a one-compartment model. PTA for the applied dosing regimen was >90% for bacteria with MIC ≤ 4 mg/L.

CONCLUSIONS

The currently approved dose of 6 g by continuous infusion may be adequate for the treatment of ventriculitis by Enterobacterales with MIC ≤ 4 mg/L if considering 100% Css>MIC as the PK/PD target to reach. Higher maintenance doses could help covering higher MICs, but their safety would need to be assessed.

Pharmacodynamics of Temocillin in Neutropenic Murine Infection Models

Temocillin is used for the treatment of various infections caused by Enterobacterales. The pharmacokinetic (PK)/pharmacodynamic (PD) index that is best correlated with the activity of beta-lactams is the percentage of time that the unbound concentration exceeds the MIC (%fT>MIC). However, the %fT>MIC needed for a bacteriostatic or killing effect of temocillin is unknown in thigh and lung infection models. In the present study, we studied the temocillin PK in plasma and epithelial lining fluid (ELF) of infected neutropenic mice and determined the plasma exposure-response relationships for Escherichia coli and Klebsiella pneumoniae. Neutropenic murine thigh and lung infection models were used. The bacterial loads in the thighs or lungs were determined. A sigmoid maximum-effect model was used to fit the plasma exposure-response relationship. A one-compartment model with first-order absorption best described temocillin PK (clearance [CL], 1.03 L/h/kg; volume of distribution [V], 0.457 L/kg). Protein binding was 78.2% ± 1.3% across different plasma concentrations. A static effect was achieved for all strains in both the thigh and lung infection models. However, the median %fT>MIC needed for a static effect was much lower in the lung infection model (27.8% for E. coli and 38.2% for K. pneumoniae) than in the thigh infection model (65.2% for E. coli and 64.9% for K. pneumoniae). A 1-log kill was reached for all strains in the lung infection model (median %fT>MIC values of 42.1% for E. coli and 44.1% for K. pneumoniae) and 7 out of 8 strains in the thigh infection model (median %fT>MIC values of 85.4% for E. coli and 74.5% for K. pneumoniae). These data support the use of temocillin in patients with pneumonia.