A Practice-Based, Clinical Pharmacokinetic Study to Inform Levetiracetam Dosing in Critically Ill Patients Undergoing Continuous Venovenous Hemofiltration (PADRE-01)

Levetiracetam dosing in continuous renal replacement therapy: A systematic review and development of a novel pharmacokinetic model to optimise dosing in critically ill patients. Do recommended doses achieve therapeutic drug concentrations?

Aim

Levetiracetam is a widely used anti-epileptic in the critical care setting that is almost exclusively (>90%) renally excreted. The altered pharmacokinetics of levetiracetam have been widely studied in intermittent haemodialysis but the evidence and guidance on dosage in continuous renal replacement therapy is varied and poorly defined. Understanding this is critical as a significant number of critically unwell patients develop renal failure requiring continuous renal replacement therapy. The aim of this systematic review is to investigate the pharmacokinetics of levetiracetam in such patients and to understand the implications on dosing strategies.

Methods

A systematic review of the available literature from 2000 to November 2022 was conducted. Seven articles were identified for inclusion from 54 records. A novel hybrid model was developed to evaluate the quality of pharmacokinetic and haemofiltration data. This data was used to develop a one-compartment model that simulated dosing strategies in 10,000 patients based on an assumed steady state of 72 hr and target trough concentrations of 12-46 mcg/mL.

Results

From the seven articles included, pharmacokinetic data was retrieved for 24 individual patients. Total clearance was 3.49-4.63 L/hr (mean 3.55, S.D. 0.52). Elimination half-life was 5.66-12.88 hr (mean 9.41, S.D. 2.86). Volume of distribution was 0.45-0.73 L/kg. The proportion of total clearance attributable to continuous renal replacement therapy was 52%-73% (mean 54.7%, S.D. 13.5). Our simulations demonstrate that more than half of patients who received twice daily doses of 750 mg or greater without a loading dose achieved therapeutic drug concentrations. The time to achievement of therapeutic drug concentrations was greatly reduced by the addition of a 60 mg/kg loading dose (up to a maximum of 4.5 g). The use of a reduced loading dose or twice daily doses of 500 mg or less without loading were more likely to result in prolonged sub-therapeutic drug concentrations.

Conclusion

Levetiracetam clearance in haemofiltration is similar to healthy adults with normal renal function (GFR > 90 mL/min). The use of reduced doses due to renal failure in critically ill patients may result in sub-therapeutic drug concentrations in a high number of patients. A twice daily dosing of 750-1000 mg with an initial loading dose of 60 mg/kg should be considered in such patients alongside therapeutic drug monitoring.

Population Pharmacokinetics-Based Evaluation of Ceftazidime-Avibactam Dosing Regimens in Critically and Non-Critically Ill Patients With Carbapenem-Resistant Klebsiella pneumoniae

Purpose

This study aimed to describe the population pharmacokinetics (PopPK) of ceftazidime-avibactam (CAZ-AVI) in adult patients, and to develop optimal dosing regimens for both non-critically ill and critically ill patients by combining different pharmacokinetic/pharmacodynamic (PK/PD) targets.

Patients and Methods

A prospective, single-center study involving patients who were infected with CRKP and received CAZ-AVI therapy was conducted. Nonlinear mixed-effect modeling was used to develop a PopPK model. The optimal dosing regimen was assessed using Monte Carlo simulation.

Results

The PopPK analysis of CAZ-AVI included 91 steady-state concentrations from 45 adult patients. The data were modeled using a one-compartment model. The typical population values of CAZ and AVI clearances were 2.96 L/h and 3.09 L/h, and the volumes of distribution were 17.76 L and 18.25 L, respectively. Our study showed that creatinine clearance (CrCL) calculated using the Cockcroft-Gault equation significantly affected the pharmacokinetics of CAZ-AVI. The Monte Carlo simulation optimized the dosing regimen for both non-critically ill and critically ill patients with varying renal functions, providing detailed supplements to the instructions.

Conclusion

Our study established a PopPK model for CAZ-AVI and proposed a reference for dosing regimen adjustment based on the severity of the disease and renal functional status.

The MILK study: Investigating intergenerational transmission of low-calorie sweeteners in breast milk

Introduction

Forty-four percent of lactating women in the United States consume beverages containing low calorie sweeteners (LCS), and the presence of LCS in the food supply has continued to increase in recent years. While LCS are approved by the United States Food and Drug Administration (FDA) and are believed to be safe for human consumption, intergenerational LCS transmission and the health impacts of early life LCS exposure are severely understudied.

Methods and analysis

In a tightly controlled, single site, prospective interventional study, mothers' plasma and breast milk, and infants' plasma will be collected from 40 mother-infant dyads over the course of 72 h, with rich sampling following maternal ingestion of a LCS sweetened beverage containing sucralose and acesulfame potassium (ace-K). Concentration-time data will be used to build maternal and infant pharmacokinetic models for future simulations and analysis.

Conclusion

This study aims to measure LCS concentrations in breast milk, maternal plasma, and infant plasma, to gain insight into infant exposure and inform recommendations for LCS consumption during breastfeeding.

Personalized antiseizure medication therapy in critically ill adult patients

Precision medicine has the potential to have a significant impact on both drug development and patient care. It is crucial to not only provide prompt effective antiseizure treatment for critically ill patients after seizures start but also have a proactive mindset and concentrate on epileptogenesis and the underlying cause of the seizures or seizure disorders. Critical illness presents different treatment issues compared with the ambulatory population, which makes it challenging to choose the best antiseizure medications and to administer them at the right time and at the right dose. Since there is a paucity of information available on antiseizure medication dosing in critically ill patients, therapeutic drug monitoring is a useful tool for defining each patient's personal therapeutic range and assisting clinicians in decision-making. Use of pharmacogenomic information relating to pharmacokinetics, hepatic metabolism, and seizure etiology may improve safety and efficacy by individualizing therapy. Studies evaluating the clinical implementation of pharmacogenomic information at the point-of-care and identification of biomarkers are also needed. These studies may make it possible to avoid adverse drug reactions, maximize drug efficacy, reduce drug-drug interactions, and optimize medications for each individual patient. This review will discuss the available literature and provide future insights on precision medicine use with antiseizure therapy in critically ill adult patients.

Pharmacokinetic considerations surrounding the use of levetiracetam for seizure prophylaxis in neurocritical care - an overview

INTRODUCTION

Levetiracetam (LEV) is one of the most widely used anti-seizure medications (ASMs) in clinical practice. This is due both to a different mechanism of action when compared to other ASMs and its easy handling. Indeed, because of its interesting pharmacokinetic properties, it is often used outside of the labeled indications, notably in the neurocritical setting as prophylaxis of epileptic seizures.

AREAS COVERED

A literature search was conducted and the most relevant studies on the pharmacokinetic properties of LEV were selected by two independent investigators. Current evidence on the use of ASM prophylaxis in the neurocritical setting was also reviewed, highlighting and discussing the strengths and limits of LEV as drug of choice for anti-epileptic prophylaxis in this scenario.

EXPERT OPINION

LEV has a 'near-ideal' pharmacokinetic profile, which makes it an attractive drug for ASM prophylaxis in neurocritical care. However, current recommendations restrict ASMs prophylaxis to very selected circumstances and the role of LEV is marginal. Moreover, studies are generally designed to compare LEV versus phenytoin, whereas studies comparing LEV versus placebo are lacking. Further, randomized trials will be needed to better elucidate LEV utility and its neuroprotective role in the neurocritical setting.

Development and Use of an Ex-Vivo In-Vivo Correlation to Predict Antiepileptic Drug Clearance in Patients Undergoing Continuous Renal Replacement Therapy

OBJECTIVES

Results from previous ex-vivo continuous renal replacement therapy (CRRT) models have successfully demonstrated similar extraction coefficients (EC) identified from in-vivo clinical trials. The objectives of this study are to develop an ex-vivo in-vivo correlation (EVIVC) model to predict drug clearance for commonly used antiepileptics and to evaluate similarity in drug extraction across different CRRT modalities to extrapolate dosing recommendations.

METHODS

Levetiracetam, lacosamide, and phenytoin CRRT clearance was evaluated using the Prismaflex CRRT system and M150 hemodiafilters using an albumin containing normal saline (ALB-NS) vehicle with 3 different albumin concentrations (2 g/dL, 3 g/dL, and 4 g/dL) and a human plasma vehicle at 3 different effluent flow rates (1 L/hr, 2 L/hr, and 3 L/hr). Blood and effluent/dialysate concentrations were collected after circuit priming. ECs were calculated for each drug, modality, vehicle, and experimental arm combination.

RESULTS

The calculated average EC for levetiracetam and lacosamide was approximated to the fraction unbound from plasma protein. Human plasma and ALB-NS vehicles demonstrated adequate prediction of in-vivo CRRT clearance. Geometric mean ratios indicated similarity in extraction coefficients when comparing between hemofiltration and hemodiafiltration modalities and between filtration and dialysis modalities at effluent flow rates ≤ 2L/hr. Evaluation of phenytoin provided inconsistent findings with regards to extraction coefficient similarity across different CRRT modalities.

CONCLUSION

The findings indicate that an ex-vivo study can be used as a surrogate to predict in-vivo levetiracetam and lacosamide clearance in patients receiving CRRT.

Population Pharmacokinetics and Dosing Optimization of Piperacillin-Tazobactam in Critically Ill Patients on Extracorporeal Membrane Oxygenation and the Influence of Concomitant Renal Replacement Therapy

Critical illness and extracorporeal circulation, such as extracorporeal membrane oxygenation (ECMO) and continuous renal replacement therapy (CRRT), may alter the pharmacokinetics of piperacillin-tazobactam. We aimed to develop a population pharmacokinetic model of piperacillin-tazobactam in critically ill patients during ECMO or CRRT and investigate the optimal dosage regimen needed to achieve ≥90% of patients attaining the piperacillin pharmacodynamic target of 100% of dosage time above MIC of 16 mg/L. This prospective observational study included 26 ECMO patients, of which 13 patients received continuous venovenous hemodiafiltration (CVVHDF). A population pharmacokinetic model was developed using nonlinear mixed-effects models, and Monte Carlo simulations were performed to evaluate creatinine clearance (CrCL) and infusion method in relation to the probability of target attainment (PTA) in four patient groups according to combination of ECMO and CVVHDF. A total of 244 plasma samples were collected. In a two-compartment model, clearance decreased during ECMO and CVVHDF contributed to an increase in the volume of distribution. The range of PTA reduction as CrCL increased was greater in the order of intermittent bolus, extended infusion, and continuous infusion method. Continuous infusion should be considered in critically ill patients with CrCL of ≥60 mL/min, and at least 12, 16, and 20 g/day was required for CrCL of <40, 40 to 60, and 60 to 90 mL/min, respectively, regardless of ECMO or CVVHDF. In patients with CrCL of ≥90 mL/min, even a continuous infusion of 24 g/day was insufficient to achieve adequate PTA. Therefore, further research on permissible high continuous infusion dose focused on the risk of toxicity is required. (This trial has been registered at ClinicalTrials.gov under registration no. NCT02581280, December 1, 2014.)

IMPORTANCE To the best of our knowledge, this is the first large prospective pharmacokinetic/pharmacodynamic (PK/PD) study of piperacillin-tazobactam in ECMO patients. We used piperacillin-tazobactam plasma concentration data from four different cases (concomitant use of ECMO and CVVHDF, receiving ECMO only, weaned from ECMO and receiving CVVHDF, and weaned from ECMO and not receiving CVVHDF) to provide preliminary insights into the incremental effects of critical illness, ECMO, and CVVHDF on PK. Our analysis revealed that volume of distribution increased in patients on CVVHDF and clearance decreased during ECMO and as creatinine clearance was reduced. When targeting 100% fT_>MIC (16 mg/L, clinical breakpoint for Pseudomonas aeruginosa), continuous infusions would have achieved the highest percentage of target attainment compared to intermittent bolus or extended infusion if the total daily dose was the same. Continuous infusion should be considered in critically ill patients with creatinine clearance of ≥60 mL/min, regardless of ECMO or CVVHDF.

A Clinician's Guide to Dosing Analgesics, Anticonvulsants, and Psychotropic Medications in Continuous Renal Replacement Therapy

Acute kidney injury (AKI) requiring continuous renal replacement therapy (CRRT) is a common complication in critical illness and has a significant impact on pharmacokinetic factors determining drug exposure, including absorption, distribution, transport, metabolism, and clearance. In this review, we provide a practical guide to drug dosing considerations in critically ill patients undergoing CRRT, focusing on the most commonly used analgesic, anticonvulsant, and psychotropic medications in the clinical care of critically ill patients. A literature search was conducted to identify articles in which drug dosing was evaluated in adult patients receiving CRRT between the years 1980 and 2020. We included articles with pharmacokinetic/pharmacodynamic analyses and those that described medication clearance via CRRT. A summary of the data focused on practical pharmacokinetic and pharmacodynamic principles is presented, with recommendations for drug dosing of analgesics, anticonvulsants, and psychotropic medications. Pharmacokinetic and pharmacodynamic studies to guide drug dosing of analgesics, anticonvulsants, and psychotropic medications in critically ill patients receiving CRRT are sparse. Considering the widespread use of these medications, narrow therapeutic index of these drug classes, and risks of over- and underdosing, additional studies in patients receiving CRRT are needed to inform drug dosing.

Levetiracetam dosing in patients receiving continuous renal replacement therapy

OBJECTIVE

The study was aimed to define appropriate levetiracetam dosing regimens from available published pharmacokinetics (PK) studies in critically ill patients with and without cirrhosis receiving continuous renal replacement therapy (CRRT) via Monte Carlo simulation (MCS).

METHODS

Mathematical pharmacokinetic models were developed using published demographic and PK data in adult critically ill patients with known variability and correlations between PK parameters. CRRT modalities (continuous venovenous hemofiltration and continuous venovenous hemodialysis) with different effluent rates were modeled. Levetiracetam regimens from available clinical resources were evaluated on the probability of target attainment (PTA) using pharmacodynamics (PD) target of the trough concentrations and area under the time-concentration curve within a range of 6-20 mg/L and 222-666 mg × hour/L for the initial 72 hours of therapy, respectively. Optimal regimens were defined from regimens that yielded the highest PTA. Each regimen was tested in a group of different 10,000 virtual patients.

RESULTS

Our results showed the optimal levetiracetam dosing regimen of 750-1000 mg every 12 hours is recommended for adult patients receiving both CRRT modalities with two different effluent rates of 25 and 35 mL/kg/h. Child-Pugh class C cirrhotic patients undergoing CRRT required lower dosing regimens of 500-750 mg every 12 ours due to smaller non-renal clearance. Of interest, some of literature-based dosing regimens were not able to attain the PK and PD targets.

SIGNIFICANCE

Volume of distribution, non-renal clearance, CRRT clearance, and body weight were significantly correlated with the PTA targets. Dosing adaptation in this vulnerable population should be concerned. Clinical validation of our finding is absolutely needed.

A prospective, real-world, clinical pharmacokinetic study to inform lacosamide dosing in critically ill patients undergoing continuous venovenous haemofiltration (PADRE-02)

AIMS

Although the use of continuous renal replacement therapy (CRRT) has increased, limited dosing information exists on the effect of CRRT on antiepileptic drug pharmacokinetics. The objectives of this practice-based study are to evaluate the pharmacokinetics of lacosamide and recommend individualized dosing recommendations in critically ill patients receiving continuous venovenous haemofiltration (CVVH).

METHODS

Seven patients receiving lacosamide and CVVH in a neurocritical care unit were enrolled. Pre-filter, post-filter and ultrafiltrate samples were obtained at baseline, right after the completion of the infusion, and up to six additional sampling time points post-administration. Patient-specific flow rates and clinical measures were also collected simultaneously at the time of sampling. Plasma concentrations were measured using a validated high-performance liquid chromatography with ultraviolet radiation detection (HPLC-UV) bioanalytical method. Non-compartmental analysis was utilized to characterize the pharmacokinetics of lacosamide.

RESULTS

The observed mean sieving coefficient for lacosamide was 0.80 ± 0.10, suggesting high removal of lacosamide. Concentrations measured in six out of seven patients were observed to be outside the therapeutic range (5-12 mg/L). The estimated average volume of distribution was found to be similar to healthy patients (0.58 L/kg). The mean bias and precision of the estimated total clearance was -2.53% and 14.9%, respectively. Simulations of various doses suggest that effluent flow rate-based dosing regimens could be used to individualize lacosamide therapeutics.

CONCLUSIONS

CVVH clearance contributed a major fraction of the total lacosamide clearance in neurocritically ill patients. Given that drug clearance increases with higher effluent flow rates, lacosamide dosing regimens should be increased to match exposures observed in patients with normal renal function.