Population Pharmacokinetics of Meropenem in Critically Ill Korean Patients and Effects of Extracorporeal Membrane Oxygenation

Meropenem Pharmacokinetics and Target Attainment in Critically Ill Patients

Purpose

This study aimed to investigate the pharmacokinetics and target attainment of meropenem and compare the effect of meropenem dosing regimens in critically ill patients.

Patients and Methods

Thirty-seven critically ill patients who were administered meropenem in intensive care units were analyzed. Patients were classified according to their renal function. Pharmacokinetic parameters were assessed based on Bayesian estimation. The target attainment of 40%fT > MIC (fraction time that the free concentration exceeds the minimum inhibitory concentration) and 100%fT > MIC with the pathogen MIC of 2 mg/L and 8 mg/L were specially focused. Furthermore, the effects of standard dosing (1g meropenem, 30 min intravenous infusion every 8h) and non-standard dosing (dosage regimens except standard dosing) were compared.

Results

The results showed that the values of meropenem clearance (CL), central volume of distribution (V1), intercompartmental clearance (Q), and peripheral volume of distribution (V2) were 3.3 L/h, 9.2 L, 20.1 L/h and 12.8 L, respectively. The CL of the patients among renal function groups was significantly different (p < 0.001). The tow targets attainment for the pathogen MIC of 2 mg/L and 8 mg/L were 89%, 73%, 49% and 27%, respectively. The severe renal impairment group has higher fraction of target attainment than the other group. The standard dosing achieved the target of 40%fT > 2/8 mg/L (85.7% and 81%, respectively) and patients with severe renal impairment achieved the target fraction of 100% for 40%fT > MIC. Additionally, there was no significant difference between standard and non-standard dosing group in target attainment.

Conclusion

Our findings indicate that renal function is an important covariate for both meropenem pharmacokinetics parameters and target attainment. The target attainment between standard and non-standard dosing group was not comparable. Therefore, therapeutic drug monitoring is indispensable in the dosing adjustment for critically ill patients if it is available.

Antimicrobial Exposures in Critically Ill Patients Receiving Extracorporeal Membrane Oxygenation

Rationale: Data suggest that altered antimicrobial concentrations are likely during extracorporeal membrane oxygenation (ECMO). Objectives: The primary aim of this analysis was to describe the pharmacokinetics (PKs) of antimicrobials in critically ill adult patients receiving ECMO. Our secondary aim was to determine whether current antimicrobial dosing regimens achieve effective and safe exposure. Methods: This study was a prospective, open-labeled, PK study in six ICUs in Australia, New Zealand, South Korea, and Switzerland. Serial blood samples were collected over a single dosing interval during ECMO for 11 antimicrobials. PK parameters were estimated using noncompartmental methods. Adequacy of antimicrobial dosing regimens were evaluated using predefined concentration exposures associated with maximal clinical outcomes and minimal toxicity risks. Measurements and Main Results: We included 993 blood samples from 85 patients. The mean age was 44.7 ± 14.4 years, and 61.2% were male. Thirty-eight patients (44.7%) were receiving renal replacement therapy during the first PK sampling. Large variations (coefficient of variation of ⩾30%) in antimicrobial concentrations were seen leading to more than fivefold variations in all PK parameters across all study antimicrobials. Overall, 70 (56.5%) concentration profiles achieved the predefined target concentration and exposure range. Target attainment rates were not significantly different between modes of ECMO and renal replacement therapy. Poor target attainment was observed across the most frequently used antimicrobials for ECMO recipients, including for oseltamivir (33.3%), piperacillin (44.4%), and vancomycin (27.3%). Conclusions: Antimicrobial PKs were highly variable in critically ill patients receiving ECMO, leading to poor target attainment rates. Clinical trial registered with the Australian New Zealand Clinical Trials Registry (ACTRN12612000559819).

Meropenem Model-Informed Precision Dosing in the Treatment of Critically Ill Patients: Can We Use It?

The number of pharmacokinetic (PK) models of meropenem is increasing. However, the daily role of these PK models in the clinic remains unclear, especially for critically ill patients. Therefore, we evaluated the published meropenem models on real-world ICU data to assess their suitability for use in clinical practice. All models were built in NONMEM and evaluated using prediction and simulation-based diagnostics for the ability to predict the subsequent meropenem concentrations without plasma concentrations (a priori), and with plasma concentrations (a posteriori), for use in therapeutic drug monitoring (TDM). Eighteen PopPK models were included for evaluation. The a priori fit of the models, without the use of plasma concentrations, was poor, with a prediction error (PE)% of the interquartile range (IQR) exceeding the ±30% threshold. The fit improved when one to three concentrations were used to improve model predictions for TDM purposes. Two models were in the acceptable range with an IQR PE% within ±30%, when two or three concentrations were used. The role of PK models to determine the starting dose of meropenem in this population seems limited. However, certain models might be suitable for TDM-based dose adjustment using two to three plasma concentrations.

Model-Informed Precision Dosing (MIPD)

Model-informed precision dosing (MIPD) is an advanced quantitative approach focusing on individualized dosage optimization, integrating complex mathematical and statistical models of drugs and disease combined with individual demographic and clinical patient characteristics [...].