Urinary Creatinine Clearance and Pharmacokinetics Studies: If We Can Measure It, Why Do We Estimate It?

Enhanced renal clearance impacts levetiracetam concentrations in patients with traumatic brain injury with and without augmented renal clearance

BACKGROUND

The purpose of this study was to examine the impact of ARC on levetiracetam concentrations during the first week following acute TBI. The hypothesis was levetiracetam concentrations are significantly lower in TBI patients with augmented renal clearance (ARC) compared to those with normal renal clearance.

METHODS

This is a prospective cohort pharmacokinetic study of adults with moderate to severe TBI treated with levetiracetam during the first week after injury. Serial blood collections were performed daily for analysis of levetiracetam, cystatin C, and 12-hr creatinine clearance (CrCl) determinations. Patients were divided into two cohorts: with (CrCl ≥130 ml/min/1.73 m2) and without ARC.

RESULTS

Twenty-two patients with moderate to severe TBI were included. The population consisted primarily of young male patients with severe TBI (mean age 40 years old, 68% male, median admission GCS 4). Each received levetiracetam 1000 mg IV every 12 h for the study period. ARC was present in 77.3% of patients, with significantly lower levetiracetam concentrations in ARC patients and below the conservative therapeutic range (< 6mcg/mL) for all study days. In patients without ARC, the serum concentrations were also below the expected range on all but two study days (Days 4 and 5). Four of the 22 (18.2%) patients exhibited seizure activity during the study period (two of these patients exhibited ARC). Cystatin C concentrations were significantly lower in patients with ARC, though the mean for all patients was within the typical normal range.

CONCLUSIONS

ARC has a high prevalence in patients with moderate to severe TBI. Levetiracetam concentrations after standard dosing were low in all TBI patients, but significantly lower in patients with ARC. This study highlights the need to consider personalized drug dosing in TBI patients irrespective of the presence of ARC.

CLINICAL TRIAL REGISTRATION

This study was registered at cliicaltrials.gov (NCT02437838) Registered on 08/05/2015, https://clinicaltrials.gov/ct2/show/NCT02437838 .

Measuring Creatinine Clearance Is the Most Accurate Way for Calculating the Proper Continuous Infusion Meropenem Dose for Empirical Treatment of Severe Gram-Negative Infections among Critically Ill Patients

Assessment of glomerular filtration rate (GFR) is necessary for dose adjustments of beta-lactam that are excreted by the kidneys, such as meropenem. The aim of this study was to compare the daily dose of 24 h-continuous infusion (CI) meropenem when GFR was calculated by means of measured creatinine clearance (mCL_CR) or estimated by the CKDEPI (eGFR_CKDEPI), Cockcroft-Gault (eGFR_CG), and MDRD (eGFR_MDRD) equations. Adult critically ill patients who underwent therapeutic drug monitoring (TDM) for the assessment of 24 h-CI meropenem steady state concentration (Css) and for whom a 24 h-urine collection was performed were retrospectively enrolled. Meropenem clearance (CL_M) was regressed against mCL_CR, and meropenem daily dose was calculated based on the equation infusion rate = daily dose/CL_M. eGFR_CKDEPI, eGFR_CG, and eGFR_CKDEPI were regressed against mCL_CR in order to estimate CL_M. Forty-six patients who provided 133 meropenem Css were included. eGFR_CKDEPI overestimated mCL_CR up to 90 mL/min, then mCL_CR was underestimated. eGFR_CG and eGFR_MDRD overestimated mCL_CR across the entire range of GFR. In critically ill patients, dose adjustments of 24 h-CI meropenem should be based on mCL_CR. Equations for estimation of GFR may lead to gross under/overestimates of meropenem dosages. TDM may be highly beneficial, especially for critically ill patients with augmented renal clearance.

Antimicrobial safety considerations in critically ill patients: part I: focused on acute kidney injury

INTRODUCTION

Antibiotic prescription is a challenging issue in critical care settings. Different pharmacokinetic and pharmacodynamic properties, polypharmacy, drug interactions, and high incidence of multidrug-resistant microorganisms in this population can influence the selection, safety, and efficacy of prescribed antibiotics.

AREAS COVERED

In the current article, we searched PubMed, Scopus, and Google Scholar for estimating renal function in acute kidney injury, nephrotoxicity of commonly used antibiotics, and nephrotoxin stewardship in intensive care units.

EXPERT OPINION

Early estimation of kidney function with an accurate method may be helpful to optimize antimicrobial treatment in critically ill patients. Different antibiotic dosing regimens may be required for patients with acute kidney injury. In many low-resource settings, therapeutic drug monitoring is not available for antibiotics. Acute kidney injury may influence treatment effectiveness and patient outcome.

Case Report: Subtherapeutic Vancomycin and Meropenem Concentrations due to Augmented Renal Clearance in a Patient With Intracranial Infection Caused by Streptococcus intermedius

Streptococcus intermedius occasionally causes brain abscesses that can be life-threatening, requiring prompt antibiotic and neurosurgical treatment. The source is often dental, and it may spread to the eye or the brain parenchyma. We report the case of a 34-year-old man with signs of apical periodontitis, endophthalmitis, and multiple brain abscesses caused by Streptococcus intermedius. Initial treatment with meropenem and vancomycin was unsuccessful due to subtherapeutic concentrations, despite recommended dosages. Adequate concentrations could be reached only after increasing the dose of meropenem to 16 g/day and vancomycin to 1.5 g × 4. The patient exhibited high creatinine clearance consistent with augmented renal clearance, although iohexol and cystatin C clearances were normal. Plasma free vancomycin clearance followed that of creatinine. A one-day dose of trimethoprim–sulfamethoxazole led to an increase in serum creatinine and a decrease in both creatinine and urea clearances. These results indicate that increased tubular secretion of the drugs was the cause of suboptimal antibiotic treatment. The patient eventually recovered, but his left eye needed enucleation. Our case illustrates that augmented renal clearance can jeopardize the treatment of serious bacterial infections and that high doses of antibiotics are needed to achieve therapeutic concentrations in such cases. The mechanisms for regulation of kidney tubular transporters of creatinine, urea, vancomycin, and meropenem in critically ill patients are discussed.