Ertapenem clearance during modeled continuous renal replacement therapy

Efficacy and safety of ertapenem dosing in patients with ESBL producing Enterobacterales infections utilizing renal replacement therapies

PURPOSE

The clinical efficacy and safety of ertapenem use in patients undergoing renal replacement therapies (RRT) are not well-documented. Therefore, we aimed to investigate the safety and efficacy of ertapenem in patients with sepsis secondary to Enterobacterales who are undergoing RRT.

METHODS

A retrospective cohort study was conducted on patients who met the inclusion criteria at our hospital between May 2015 and December 2021. The primary endpoint was 30-day mortality. Secondary endpoints included clinical cure, microbiologic cure, recurrence rate, and incidence of seizures.

RESULTS

During the study period, 158 patients met the inclusion criteria. Of these, 86 were male (54.4%), the mean age was 66.4 ± 13.8 years, and the mean weight was 77 ± 22.4 kg. The most common diagnosis was bacteremia in 48 (30.4%) subjects, followed by urinary tract infection in 39 (24.7%) subjects, and pneumonia in 35 (22.2%) patients. The most isolated pathogens were Escherichia coli, followed by Klebsiella species. The median ertapenem dose was 0.5 g intravenously (IV) daily in those who received intermittent hemodialysis (IHD) and 1 g IV daily for those who received continuous veno-venous hemofiltration (CVVH). The 30-day mortality rate was 24%, the clinical cure rate was 89.2%, the microbiologic cure rate was 82%, the 30-day recurrence rate was 41.1%, and the incidence of seizures was 2.5%. Multivariate logistic regression analysis indicated that age (OR 1.04 [95% CI: 1.003-1.075]), being critically ill at therapy initiation (OR 2.9 [95% CI: 1.1-7.5]), and Enterobacterales other than Klebsiella species and Escherichia coli (OR 3.8 [95% CI: 1.1-12.5]) were significant independent risk factors associated with mortality in this population. Ertapenem dose was not associated with mortality.

CONCLUSION

Our findings suggest that the commonly used doses of ertapenem in patients undergoing IHD and CVVH are clinically effective but may pose a higher risk of seizures. A comprehensive pharmacokinetic study is needed to determine the most effective and safe dose for this population.

Determination of ertapenem in plasma and ascitic fluid by UHPLC-MS/MS in cirrhotic patients with spontaneous bacterial peritonitis

Objectives

Spontaneous bacterial peritonitis is a frequent severe complication in cirrhotic patients with ascites. Carbapenem antibiotics are currently the treatment of choice for patients with hospital-acquired or healthcare-related infections. However, there is limited evidence available on the efficacy of ertapenem in cirrhotic patients with spontaneous bacterial peritonitis. As a result, the pharmacokynetics and pharmacodynamics of this antibiotic are still unknown. The objective of this study was to develop and validate measurement procedures based on liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) to determine ertapenem concentrations in plasma and ascitic fluid.

Methods

Samples were pretreated by acetronile protein-precipitation. Chromatographic separation is performed on a C18 reversed-phase Acquity®-UPLC®-BEHTM column (2.1 × 100 mm id, 1.7 µm) using a non-linear gradient of water/acetonitrile containing 0.1 % of formic acid at a flow rate of 0.4 mL/min. Ertapenem and its internal standard (ertapenem-D4) are detected by tandem mass spectrometry using positive electrospray ionization and multiple reaction monitoring, and using 476.2 → 346.0/432.2 as mass transition for ertapenem and 480.2 → 350.0 for its internal standard.

Results

No significant interferences or carry-over contamination were observed. Imprecisions, absolute relative bias, matrix effects and normalized recoveries were ≤14.5 %, ≤9.3 % (92.8-104.5) % and (98.8-105.8) %, respectively. Chromatographic measurement procedures were linear from (0.50-100) mg/L.

Conclusions

The measurement procedures based on UHPLC-MS/MS developed and validated in this study could be useful in pharmacokynetic and pharmacodynamic studies in subjects with liver cirrhosis who develop spontaneous bacterial peritonitis treated with ertapenem.

Medición de la concentración de ertapenem en el plasma y líquido ascítico mediante UHPLC-MS/MS. Aplicación en pacientes cirróticos con peritonitis bacteriana espontánea

Objetivos

La peritonitis bacteriana espontánea es una complicación frecuente y grave de los pacientes cirróticos con ascitis. Actualmente, los antibióticos carbapenémicos son el tratamiento de elección en pacientes con peritonitis nosocomiales o relacionadas con el sistema sanitario. Pese a ello, los estudios de eficacia del ertapenem en pacientes cirróticos con peritonitis bacteriana espontánea son limitados y la farmacocinética y farmacodinamia de este antibiótico continúa siendo desconocida. Así, el objetivo de este estudio es desarrollar y validar procedimientos de medida basados en la cromatografía líquida de alta y rápida eficacia acoplada a la espectrometría de masas en tándem (UHPLC-MS/MS) para medir las concentraciones de ertapenem en el plasma y en el líquido ascítico.

Métodos

El pretratamiento de las muestras se realiza utilizando una precipitación de proteínas con acetonitrilo. La separación cromatográfica se lleva a cabo en una columna C18 de fase inversa Acquity®-UPLC®-BEHTM (2,1 × 100 mm id, 1,7 µm) utilizando un gradiente no lineal de agua/acetonitrilo que contiene un 0,1 % de ácido fórmico y an un flujo de 0,4 mL/min. El ertapenem y su patrón interno (ertapenem-D4) son detectados mediante espectrometría de masas en tándem en las modalidades de ionización mediante electroespray positiva y de monitorización múltiple de reacción utilizando, como transiciones de masa, 476,2→346,0/432,2 para el ertapenem y 480,2→350,0 para su patrón interno.

Resultados

No se observan interferencias ni contaminación por arrastre significativas. Las imprecisiones, los sesgos relativos absolutos, así como los efectos matriz y recuperaciones normalizadas son ≤14,5 %, ≤9,3 %, (92,8−104,5) % y (98,8−105,8) %, respectivamente. Los procedimientos de medida cromatográficos son lineales entre (0,50−100) mg/L.

Conclusiones

Los procedimientos de medida basados en la UHPLC-MS/MS desarrollados y validados podrían ser de utilidad para realizar estudios farmacocinéticos y farmacodinámicos en sujetos con cirrosis hepática que presentan peritonitis bacteriana espontánea tratados con ertapenem.

Adsorption and Clearance of the Novel Fluorescent Tracer Agent MB-102 During Continuous Renal Replacement Therapy: In Vitro Results

MB-102 is a novel fluorescent tracer agent that is exclusively removed from the body by glomerular filtration. This agent can be detected transdermally to provide a real-time measurement of glomerular filtration rate at the point-of-care and is currently in clinical studies for such. MB-102 clearance during continuous renal replacement therapy (CRRT) is unknown. Its plasma protein binding (~0%), molecular weight (~372 Da) and volume of distribution (15-20 L) suggest that it may be removed by renal replacement therapies. To determine the disposition of MB-102 during CRRT, an in vitro study assessing the transmembrane clearance (CL TM ) and adsorptive clearance of MB-102 was conducted. A validated in vitro bovine blood continuous hemofiltration (HF) and continuous hemodialysis (HD) models were performed using two types of hemodiafilters to evaluate CL TM of MB-102. For HF, three different ultrafiltration rates were evaluated. For HD, four different dialysate flow rates were evaluated. Urea was used as a control. No MB-102 adsorption to the CRRT apparatus or either of hemodiafilters was observed. MB-102 is readily removed by HF and HD. Dialysate and ultrafiltrate flow rates directly influence MB-102 CLTM. Hence MB-102 CLTM should be measurable for critically ill patients receiving CRRT.

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.

Recommendation of Antimicrobial Dosing Optimization During Continuous Renal Replacement Therapy

Continuous Renal Replacement Therapy (CRRT) is more and more widely used in patients for various indications recent years. It is still intricate for clinicians to decide a suitable empiric antimicrobial dosing for patients receiving CRRT. Inappropriate doses of antimicrobial agents may lead to treatment failure or drug resistance of pathogens. CRRT factors, patient individual conditions and drug pharmacokinetics/pharmacodynamics are the main elements effecting the antimicrobial dosing adjustment. With the development of CRRT techniques, some antimicrobial dosing recommendations in earlier studies were no longer appropriate for clinical use now. Here, we reviewed the literatures involving in new progresses of antimicrobial dosages, and complied the updated empirical dosing strategies based on CRRT modalities and effluent flow rates. The following antimicrobial agents were included for review: flucloxacillin, piperacillin/tazobactam, ceftriaxone, ceftazidime/avibactam, cefepime, ceftolozane/tazobactam, sulbactam, meropenem, imipenem, panipenem, biapenem, ertapenem, doripenem, amikacin, ciprofloxacin, levofloxacin, moxifloxacin, clindamycin, azithromycin, tigecycline, polymyxin B, colistin, vancomycin, teicoplanin, linezolid, daptomycin, sulfamethoxazole/trimethoprim, fluconazole, voriconazole, posaconzole, caspofungin, micafungin, amphotericin B, acyclovir, ganciclovir, oseltamivir, and peramivir.

Influence of hemodialysis on regadenoson clearance in an in vitro hemodialysis model

BACKGROUND

Regadenoson is a novel pharmacological stress agent whose disposition during hemodialysis is not known. The purpose of this study was to determine the clearance of regadenoson under varying dialytic conditions using an in vitro hemodialysis model.

METHODS AND RESULTS

Whole human blood was used to analyze the effect of hemodialysis on the clearance of regadenoson. Regadenoson transmembrane clearance (CLD) was assessed for both a standard permeability and a high permeability polysulfone hemodialyzer with blood/dialysate flow rates of 300/600 and 400/800 mL/min. A two-tailed, paired Student's t test was used to compare regadenoson CLD between hemodialyzer types and flow rates. The mean ± SD regadenoson CLD values ranged between 62.5 ± 11.8 and 89.1 ± 24.0 mL/min for all dialytic conditions. There was no significant difference in regadenoson CLD between hemodialyzer types and flow rates (p > .05).

CONCLUSIONS

Hemodialysis enhances the clearance of regadenoson independent of hemodialyzer permeability and blood/dialysate flow rate. This clearance is modest relative to total body clearance and is unlikely to produce a clinically significant outcome.

Telavancin and Hydroxy Propyl-β-Cyclodextrin Clearance during Continuous Renal Replacement Therapy: An in vitro Study

Background/Aims

Telavancin is a lipoglycopeptide antimicrobial agent which has been approved in Europe and has been recently FDA approved in the United States. Telavancin's parenteral solution contains hydroxy propyl-β-cyclodextrin (HP-β-CD) to enhance its solubility. The disposition of telavancin and HP-β-CD during continuous renal replacement therapies (CRRT) has not been previously reported.

Methods

The transmembrane clearances (CLtm) of telavancin and HP-β-CD during continuous hemofiltration and hemodialysis were assessed using an in vitro bovine blood model with AN69 and polysulfone hemodiafilters at varying ultrafiltrate and dialysate flow rates (1, 2, 3, & 6 l/hr).

Results

The mean telavancin sieving coefficient ranged from 0.25 to 0.31 during continuous hemofiltration. At all ultrafiltration rates, no differences were observed in telavancin CLtm between the two hemodiafilter types. For continuous hemodialysis, mean telavancin saturation coefficients ranged from 0.10 to 0.43 and CLtm tended to be higher for the polysulfone hemodiafilter than the AN69 hemodiafilter, especially at higher flow rates. Mean HP-β-CD sieving coefficients ranged from 0.63 to 1.03 and saturation coefficients from 0.63 to 1.38, resulting in a CLtm that was similar to ultrafiltrate and dialysate flow rates.

Conclusion

Telavancin CLtm is dependent on hemodiafilter type, dialysate and ultrafiltration rates. CRRT with high ultrafiltrate or dialysate rates may result in sufficient telavancin clearance to alter telavancin dosing. HP-β-CD clearance by continuous hemodialysis or continuous hemofiltration is substantial and may be sufficient to prevent HP-β-CD accumulation in subjects receiving CRRT. Pharmacokinetic studies conducted in patients receiving CRRT and telavancin are needed to confirm these in vitro findings.

Acetaminophen clearance during ex vivo continuous renal replacement therapies

Intravenous acetaminophen is an adjuvant to opioid use in critically ill and surgical patients requiring continuous renal replacement therapy (CRRT). The objective of this study was to determine the ex vivo transmembrane clearance of intravenous acetaminophen during continuous hemofiltration and hemodialysis. Transmembrane clearance was assessed using a validated ex vivo bovine blood model for CRRT using an F8 or HF1400 hemodiafilter. Ultrafiltrate and dialysate flow rates were 1, 2, and 3 L/h. Urea and acetaminophen clearances were calculated and compared. Acetaminophen was readily cleared by continuous hemofiltration with both hemodiafilters. Acetaminophen clearance rates were 92-98% of ultrafiltrate production rates. Similarly, dialytic acetaminophen clearances approximated dialysate flow rates for both hemodiafilters. Acetaminophen is readily cleared by CRRT. Patients receiving CRRT and acetaminophen may require increased doses for adequate pain control.

Can we use an ex vivo continuous hemofiltration model to describe the adsorption and elimination of meropenem and piperacillin?

OBJECTIVES

To determine the adsorption and elimination characteristics of meropenem and piperacillin during simulated continuous renal replacement therapy (CRRT), and to compare the observed data from this ex vivo study with previous data from clinical studies.

METHOD

This was an experimental study utilizing a modified CRRT circuit and polysulfone membrane (1.2 m2), circulated with a blood-crystalloid mixture. Adsorption onto the CRRT circuit was tested over a 4-h period, and clearance was assessed separately using variable continuous hemofiltration settings.

RESULTS

A rapid 9% reduction in circulating meropenem and piperacillin concentrations was observed at approximately 0.5 and 1.0 h for each antibiotic, respectively. The post-dilution setting was associated with a significantly higher sieving coefficient (Sc) and filter clearance (CLfilter) (mean ± SD) (Sc 1.14 ± 0.10 versus 1.06 ± 0.04; CLfilter 19.05 ± 1.63 versus 17.59 ± 0.62 ml/min, P values < 0.05) for meropenem. No significant differences were observed for piperacillin pharmacokinetics. Clinically comparable Sc data were observed between data obtained from the ex vivo study and data from previous clinical studies, for both antibiotics.

CONCLUSIONS

Meropenem and piperacillin appear to be rapidly adsorbed into the CRRT circuit, and the delivery site of fluid replacement significantly influences meropenem pharmacokinetics. However, these findings are likely to be clinically insignificant and not affect dosing requirements. This ex vivo method could be a surrogate for future clinical pharmacokinetic studies of CRRT. Further research is required to explore the applicability of the ex vivo method to further characterize antibiotic pharmacokinetics during CRRT.

Principles and operational parameters to optimize poison removal with extracorporeal treatments

A role for nephrologists in the management of a poisoned patient involves evaluating the indications for, and methods of, enhancing the elimination of a poison. Nephrologists are familiar with the various extracorporeal treatments (ECTRs) used in the management of impaired kidney function, and their respective advantages and disadvantages. However, these same skills and knowledge may not always be considered, or applicable, when prescribing ECTR for the treatment of a poisoned patient. Maximizing solute elimination is a key aim of such treatments, perhaps more so than in the treatment of uremia, because ECTR has the potential to reverse clinical toxicity and shorten the duration of poisoning. This manuscript reviews the various principles that govern poison elimination by ECTR (diffusion, convection, adsorption, and centrifugation) and how components of the ECTR can be adjusted to maximize clearance. Data supporting these recommendations will be presented, whenever available.

Pharmacokinetics of ertapenem in critically ill patients receiving continuous venovenous hemodialysis or hemodiafiltration

This study characterizes the pharmacokinetics of ertapenem, a carbapenem antibiotic, in critically ill adult subjects receiving continuous renal replacement therapy (CRRT). Eight critically ill patients with suspected/known Gram-negative infections receiving continuous venovenous hemodialysis (CVVHD) or continuous venovenous hemodiafiltration (CVVHDF) and ertapenem were enrolled. One gram of ertapenem was infused over 30 min. Predialyzer blood samples were drawn with the first dose of ertapenem from the hemodialysis tubing at time zero, 30 min, and 1, 2, 4, 8, 12, 18, and 24 h after the start of the ertapenem infusion. Effluent was collected at the same time points. Ertapenem total serum, unbound serum, and effluent concentrations from all eight subjects were used simultaneously to perform a population compartmental pharmacokinetic modeling procedure using NONMEM. Monte Carlo simulations were performed to evaluate the ability of several ertapenem dosing regimens (500 mg once daily, 750 mg once daily, 500 mg twice daily, and 1,000 mg once daily) to obtain effective unbound serum concentrations above 0.5, 1, and 2 μg/ml. For our simulated patients, all regimens produced unbound ertapenem concentrations above 2 μg/ml for 40% of the dosing interval for at least 96% of simulated patients. (This study has been registered at ClinicalTrials.gov under registration no. NCT00877370.).

In vitro glucose kinetics during continuous renal replacement therapy: implications for caloric balance in critically ill patients

PURPOSE

To examine the impact of continuous renal replacement therapy (CRRT) on glucose kinetics and therefore caloric balance.

METHODS

In vitro experiments were conducted to characterize glucose kinetics in a variety of CRRT modalities and prescriptions. Additional experiments evaluated the impact of citrate anticoagulation using anti-coagulant dextrose solution A (ACD-A) on CRRT glucose movement. A formula was developed to predict the glucose delivery to/from the patient per day of CRRT, and this data was extrapolated to determine the net caloric impact of CRRT.


RESULTS

A total of 104 experiments were conducted with an overall glucose extraction coefficient of 1.04 (95% CI 1.03-1.05). CRRT-related glucose removal was directly related to effluent (dialysate and/or hemofiltration) rate and pre-filter blood glucose concentration, and inversely related to dialysis solution glucose concentration. In all modalities tested, CRRT resulted in a net negative glucose balance, with estimated caloric losses ranging between 20 kcal and 550 kcal depending on the conditions tested. The addition of ACD-A resulted in net glucose delivery in some conditions and a positive caloric balance of up to 470 kcal per day.

CONCLUSIONS

CRRT can have a significant effect on glucose balance and result in either significant daily caloric gains or losses, and this effect can be predicted based on CRRT prescription and patient characteristics. Clinicians should be aware of this potential impact when prescribing nutritional therapy to patients undergoing CRRT, as an imbalance in caloric feeding can adversely affect outcomes in critically ill patients.

Vibration enhances clearance of solutes with varying molecular weights during in vitro hemodialysis

This proof of concept pilot study was performed to determine whether vibration can increase solute clearance when applied to an in vitro dialysis model. Urea, creatinine, gentamicin, and vancomycin transmembrane clearances were calculated at a blood flow rate of 200 ml/min, dialysate flow rates of 2 and 8 L/hr, and no concurrent ultrafiltration at various vibration intensities. Dialyzer integrity was determined by measuring transmembrane pressure, filter drop pressure, and albumin clearance, and by visually inspecting the dialysate. Comparing the highest vibration modality with no vibration, the median percentage increase in urea, creatinine, gentamicin, and vancomycin clearance was 18% (all p < 0.005). The transmembrane clearance of albumin was negligible for all experiments. When measuring transmembrane pressure and filter drop pressure, no significant differences were found between nonvibration and vibration dialysis. The addition of vibration during dialysis increased transmembrane clearance for solutes with molecular weights of 60-1450 Daltons.

Use of an in vitro model of renal replacement therapy systems to estimate extracorporeal drug removal

The use of in vitro modeling to predict in vivo drug and solute clearance during renal replacement therapy has evolved to reflect the different dialytic therapies available in clinical practice. This area of renal replacement therapy research is representative of translational research that demonstrates a correlation from bench to bedside where results generated in the laboratory can assist with clinical decisions in the absence of in vivo studies. This review describes in vitro renal replacement therapy models and compares the findings of several in vitro and in vivo studies.

Longitudinal hemodiafilter performance in modeled continuous renal replacement therapy

BACKGROUND/AIMS

With advanced anticoagulation, many institutions operate continuous renal replacement therapy (CRRT) circuits longer than manufacturers' recommendations. This extended use may change hemodiafilter performance and clearance properties. However, hemodiafilter performance over time has not been assessed. We investigated solute clearance over time in modeled CRRT.

METHODS

In vitro continuous hemofiltration (CH) and continuous hemodialysis (CD) were operated for 48 h using AN69 polyacrylonitrile, cellulose triacetate, F70 polysulfone, and Optiflux F160NR polysulfone hemodiafilters with citrated bovine blood. Urea, creatinine, gentamicin, vancomycin, and albumin clearances were assessed in CH (ultrafiltration rates = 1 and 3 l/h). Clearances of urea, creatinine, gentamicin, and albumin, were assessed in CD with dialysate flow rate of 2 l/h.

RESULTS

Solute CH clearances were significantly higher at 3 l/h. Only creatinine and gentamicin clearances were affected by time. Creatinine CD clearance significantly declined at 48 h for all hemodiafilters, especially polysulfone hemodiafilters.

CONCLUSIONS

CRRT duration affects solute transmembrane clearance. Clinicians should consider hemodiafilter age when assessing hemodialysis dose or drug clearance.

Influence of continuous venovenous hemofiltration and continuous venovenous hemodiafiltration on the disposition of doripenem

The pharmacokinetics, safety, and tolerability of a single 1-hour, 500-mg intravenous infusion of doripenem were assessed in dialysis-dependent subjects with stage 5 chronic kidney disease undergoing continuous renal replacement therapy (CRRT) via 12-hour continuous venovenous hemofiltration (CVVH) (n = 6) or continuous venovenous hemodiafiltration (CVVHDF) (n = 5). Healthy volunteers were also assessed (n = 12). Concentrations of doripenem and the primary metabolite doripenem-M-1 were measured in plasma and ultrafiltrate or ultrafiltrate/dialysate by a validated liquid chromatography-tandem mass spectrometry method. In dialysis-dependent subjects, levels of systemic exposure to doripenem and doripenem-M-1 were approximately 3- and 5-fold greater, respectively, than those in healthy subjects: for doripenem, 98 μg·h/ml for CVVH and 77 μg·h/ml for CVVHDF versus 32 μg·h/ml for healthy subjects, and for doripenem-M-1, 24 μg·h/ml for CVVH and 22 μg·h/ml for CVVHDF versus 4.7 μg·h/ml for healthy subjects. The mean sieving coefficients and saturation coefficients were >0.67 for both doripenem and doripenem-M-1. During CVVH and CVVHDF, respectively, the percentages of administered doripenem dose removed were 38% and 29%, and clearances of doripenem were 22 and 25 ml/min. Both CVVH and CVVHDF efficiently removed doripenem and doripenem-M-1. Despite significant removal of drug by CVVH and CVVHDF, a single 1-hour, 500-mg doripenem infusion produced significantly higher plasma concentrations of doripenem, higher systemic exposure (area under the plasma concentration-time curve from time zero to 12 h after the start of infusion [AUC(0-12)]), and longer half-life (t(1/2)) in subjects receiving CVVH or CVVHDF than in healthy volunteers. The recovery of drug in ultrafiltrate and ultrafiltrate/dialysate and the enhanced rate of reduction of plasma concentrations indicate that CVVH and CVVHDF significantly augmented residual total body clearance of doripenem in subjects receiving CRRT. Doripenem dosage regimens for patients receiving CRRT thus need to be adjusted.

Using drug probes to monitor hepatic drug metabolism in critically ill patients: midazolam, a flawed but useful tool for clinical investigation of CYP3A activity?

IMPORTANCE OF THE FIELD

In the UK, acute kidney injury (AKI) occurs in 25% of patients admitted to intensive care. Outcome is worsened in the presence of AKI for reasons not easily explained. AKI unpredictably affects the pharmacokinetics and pharmacodynamics of drugs and dosing in patients with AKI is largely based on data from chronic kidney disease patients, but how appropriately is unknown.

AREAS COVERED IN THIS REVIEW

Midazolam as a drug probe of CYP3A activity is reviewed, with discussion of its limitations and alternatives in critically ill patients. Pharmacogenetics of CYP3A enzymes and their significance are discussed and emerging evidence that AKI affects liver metabolism is reviewed.

WHAT THE READER WILL GAIN

The aim is to give the reader insight into the complexities of in vivo research in critically ill patient with discussion of interaction between the kidney and liver. We explain the use of midazolam as a drug probe for the investigation of the effect of AKI on hepatic function.

TAKE HOME MESSAGE

Critically ill patients are difficult to manage but methods are now available for investigation of complex interrelationships that complicate the care and management of these patients with the potential to improve safety, efficacy and outcome, particularly for drug administration.

Challenges in developing evidence-based drug dosing guidelines for adults and children receiving renal replacement therapy

The challenges of appropriate drug dosing in patients with renal failure requiring renal replacement therapy (RRT) have been exacerbated by recent trends in both RRT technology and practices. Nearly all these changes have resulted in augmented drug clearance, making most existing RRT drug dosing recommendations obsolete. Many barriers exist to conducting research to update our knowledge of appropriate drug dosing in the context of contemporary RRT. Recommendations on how this research could be conducted, including the use of in vitro techniques, are offered here.