Pharmacokinetics and clearance of ganciclovir during continuous hemodiafiltration

Valganciclovir Dosing for Cytomegalovirus Prophylaxis in Solid-organ Transplant Recipients on Continuous Veno-venous Hemodialysis

BACKGROUND

Optimal valganciclovir dosing for cytomegalovirus (CMV) prophylaxis in solid-organ transplant (SOT) patients on continuous veno-venous hemodialysis (CVVHD) is not known. Ganciclovir trough concentrations ≥0.60 μg/mL have been suggested for CMV prophylaxis. This study was conducted to determine if valganciclovir 450 mg enterally every 24 hours achieves ganciclovir trough concentrations ≥0.60 μg/mL in patients on CVVHD.

METHODS

This single-center, prospective, open-label, pharmacokinetic study included adult SOT patients admitted to an intensive care unit from March 2018 to June 2019 on CVVHD. All patients were receiving valganciclovir 450 mg enterally every 24 hours for CMV prophylaxis prior to enrollment. Each patient had a peak and trough sample drawn at steady state.

RESULTS

Ten SOT patients were included in the study (6 liver, 1 simultaneous liver-kidney, 2 bilateral lung, 1 heart). The mean ± SD age was 51.8 ± 14.0 years, and average body mass index was 27 ± 6.9 kg/m2. Ganciclovir trough concentrations ranged from 0.31 to 3.16 μg/mL, and 80% of participants have trough concentrations ≥0.60 μg/mL. No patients had documented neutropenia while on valganciclovir and CVVHD; 60% of patients had significant thrombocytopenia.

CONCLUSIONS

Valganciclovir 450 mg enterally every 24 hours achieved ganciclovir trough concentrations ≥0.60 μg/mL in most patients on CVVHD, similar to those reported with intravenous ganciclovir for prophylaxis in this population. Based on these data, valganciclovir may require dosing every 24 hours to achieve concentrations equivalent to ganciclovir. Neutropenia did not occur in the study period. Thrombocytopenia was common and likely multifactorial.

The Effects of Continuous Renal Replacement on Anti-infective Therapy in the Critically Ill

Acute renal failure represents a frequent, severe complication in critically ill patients leading to a direct increase in mortality and resource utilization. Today, continuous renal replacement therapy (CRRT) has replaced traditional hemodialysis, providing more precise fluid and metabolic control and decreased hemodynamic instability. There are a limited number of studies conducted for the ideal dosing of individual anti-infective agents for patients receiving CRRT. However, knowledge of the basic principles of CRRT, in conjunction with pharmacokinetics and pharmacodynamics of anti-infectives, allows sound dosing recommendations to be formulated to ensure maximal killing effects with minimal risk of toxicity in patients receiving CRRT.

Clinical pharmacokinetics and pharmacodynamics of ganciclovir and valganciclovir in children with cytomegalovirus infection

INTRODUCTION

Among infants and immunocompromised children cytomegalovirus (CMV) is associated with significant morbidity and mortality.

AREAS COVERED

This review describes the clinical pharmacokinetics and pharmacodynamics of ganciclovir and valganciclovir for the treatment and prevention of CMV infection in children.

EXPERT OPINION

A 24-h ganciclovir area under the concentration versus time curve (AUC₀₋₂₄) of 40 - 60 μg h/ml decreased the risk of CMV infection for adults undergoing CMV prophylaxis. For adults undergoing treatment for active CMV disease, a target AUC₀₋₁₂ of 40 - 60 μg h/ml has been suggested. The applicability of these targets to children remains uncertain; however, with the most sophisticated dosing regimens developed to date only 21% of patients are predicted to reach these targets. Moving forward, identification of optimal pediatric ganciclovir and valganciclovir dosing regimens may involve the use of an externally validated pediatric population pharmacokinetic model for empirical dosing, an optimal sampling strategy for collecting a minimal number of blood samples for each patient and Bayesian updating of the dosing regimen based on an individual patient's pharmacokinetic profile.

Pharmacokinetics of ganciclovir during continuous venovenous hemodiafiltration in critically ill patients

Ganciclovir is an antiviral agent that is frequently used in critically ill patients with cytomegalovirus (CMV) infections. Continuous venovenous hemodiafiltration (CVVHDF) is a common extracorporeal renal replacement therapy in intensive care unit patients. The aim of this study was to investigate the pharmacokinetics of ganciclovir in anuric patients undergoing CVVHDF. Population pharmacokinetic analysis was performed for nine critically ill patients with proven or suspected CMV infection who were undergoing CVVHDF. All patients received a single dose of ganciclovir at 5 mg/kg of body weight intravenously. Serum and ultradiafiltrate concentrations were assessed by high-performance liquid chromatography, and these data were used for pharmacokinetic analysis. Mean peak and trough prefilter ganciclovir concentrations were 11.8 ± 3.5 mg/liter and 2.4 ± 0.7 mg/liter, respectively. The pharmacokinetic parameters elimination half-life (24.2 ± 7.6 h), volume of distribution (81.2 ± 38.3 liters), sieving coefficient (0.76 ± 0.1), total clearance (2.7 ± 1.2 liters/h), and clearance of CVVHDF (1.5 ± 0.2 liters/h) were determined. Based on population pharmacokinetic simulations with respect to a target area under the curve (AUC) of 50 mg · h/liter and a trough level of 2 mg/liter, a ganciclovir dose of 2.5 mg/kg once daily seems to be adequate for anuric critically ill patients during CVVHDF.

Presence and accuracy of drug dosage recommendations for continuous renal replacement therapy in tertiary drug information references

BACKGROUND

Clinicians commonly rely on tertiary drug information references to guide drug dosages for patients who are receiving continuous renal replacement therapy (CRRT). It is unknown whether the dosage recommendations in these frequently used references reflect the most current evidence.

OBJECTIVE

To determine the presence and accuracy of drug dosage recommendations for patients undergoing CRRT in 4 drug information references.

METHODS

Medications commonly prescribed during CRRT were identified from an institutional medication inventory database, and evidence-based dosage recommendations for this setting were developed from the primary and secondary literature. The American Hospital Formulary System-Drug Information (AHFS-DI), Micromedex 2.0 (specifically the DRUGDEX and Martindale databases), and the 5th edition of Drug Prescribing in Renal Failure (DPRF5) were assessed for the presence of drug dosage recommendations in the CRRT setting. The dosage recommendations in these tertiary references were compared with the recommendations derived from the primary and secondary literature to determine concordance.

RESULTS

Evidence-based drug dosage recommendations were developed for 33 medications administered in patients undergoing CRRT. The AHFS-DI provided no dosage recommendations specific to CRRT, whereas the DPRF5 provided recommendations for 27 (82%) of the medications and the Micromedex 2.0 application for 20 (61%) (13 [39%] in the DRUGDEX database and 16 [48%] in the Martindale database, with 9 medications covered by both). The dosage recommendations were in concordance with evidence-based recommendations for 12 (92%) of the 13 medications in the DRUGDEX database, 26 (96%) of the 27 in the DPRF5, and all 16 (100%) of those in the Martindale database.

CONCLUSIONS

One prominent tertiary drug information resource provided no drug dosage recommendations for patients undergoing CRRT. However, 2 of the databases in an Internet-based medical information application and the latest edition of a renal specialty drug information resource provided recommendations for a majority of the medications investigated. Most dosage recommendations were similar to those derived from the primary and secondary literature. The most recent edition of the DPRF is the preferred source of information when prescribing dosage regimens for patients receiving CRRT.

[Study of factors affecting drug extraction during continuous hemofiltration and hemodiafiltration, and the contribution of extraction to systemic clearance]

The aim of this study was to elucidate the factors affecting dialysis clearance and the need for additional doses of drugs during and after continuous hemofiltration (CHF) and hemodiafiltration (CHDF). We performed a literature search of MEDLINE using the terms hemofiltration OR hemodiafiltration AND pharmacokinetics to obtain the clearances of CHF and CHDF in a clinical setting. The relationships between molecular weight, the unbound fraction (fuB), ultrafiltration flow rate (UFR) and dialysis flow rate were analyzed. The need for additional doses of certain drugs was also discussed based on the ratio of dialysis and systemic clearances. The clearance of CHF for 32 reported drugs was significantly correlated with the product of fuB×UFR (r=0.841, p<0.001), and furthermore the plots obtained lay on a line of y=x. The clearance of CHDF also showed good correlation with the product of fuB×UFR (r=0.795, p<0.001), but the plots were higher than the line for y=x, suggesting that additional clearance by dialysis was not negligible. The elimination by both forms of dialysis for drugs excreted mainly via the kidneys, and with a higher fuB, was considerable. The extent of drug clearance by both CHF and CHDF is determined mainly by fuB and UFR. The ratio of dialysis clearance to systemic clearance should be estimated to determine the contribution of CHF and CHDF.

Quality of pharmacokinetic studies in critically ill patients receiving continuous renal replacement therapy

Continuous renal replacement therapy (CRRT) is the preferred renal replacement therapy modality in the critically ill. We aimed to reveal the literature on the pharmacokinetic studies in critically ill patients receiving CRRT with special reference to quality assessment of these studies and the CRRT dose. We conducted a systematic review by searching the MEDLINE, EMBASE, and the Cochrane databases to December 2009 and bibliographies of relevant review articles. We included original studies reporting from critically ill adult subjects receiving CRRT because of acute kidney injury with a special emphasis on drug pharmacokinetics. We used the minimum reporting criteria for CRRT studies by Acute Dialysis Quality Initiative (ADQI) and, second, the Downs and Black checklist to assess the quality of the studies. We calculated the CRRT dose per study. We included pharmacokinetic parameters, residual renal function, and recommendations on drug dosing. Of 182 publications, 95 were considered relevant and 49 met the inclusion criteria. The median [interquartile range (IQR)] number of reported criteria by ADQI was 7.0 (5.0-8.0) of 12. The median (IQR) Downs and Black quality score was 15 (14-16) of 32. None of the publications reported CRRT dose directly. The median (IQR) weighted CRRT dose was 23.7 (18.8-27.9) ml/kg/h. More attention should be paid both to standardizing the CRRT dose and reporting of the CRRT parameters in pharmacokinetic studies. The general quality of the studies during CRRT in the critically ill was only moderate and would be greatly improved by reports in concordant with the ADQI recommendations.

[Drugs dosing in intensive care unit during continuous renal replacement therapy]

Drug dosing in the intensive care unit can be challenging. Acute kidney injury (AKI) is a common complication of sepsis and a part of multiple organ dysfunction syndrome. Continuous renal replacement therapy (CRRT) is increasingly used as dialysis therapy in this critically ill population. Available data demonstrate that sepsis, AKI and different modalities of CRRT can profoundly change drugs pharmacokinetic. The severity of these changes depends on molecules characteristics (volume of distribution, plasma protein binding, molecular weight, plasma half-life, plasma clearance), patient itself (volemia, residual renal function, tissue perfusion, hepatic dysfunction) and modality of CRRT (diffusion, convection, adsorption). There are no available recommendations to adapt drug dosing in a given critically ill patient with a given modality of CRRT. It is necessary to fully understand the different methods of CRRT and drug pharmacokinetic to prescribe the appropriate dose and to avoid under or potentially toxic overdosing. Monitoring the plasma level of drug - when available - can establish a relation between the blood concentration and its effect; thus, facilitating drug dosing.

Drug dosing during intermittent hemodialysis and continuous renal replacement therapy : special considerations in pediatric patients

Chronic renal failure is, fortunately, an unusual occurrence in children; however, many children with various underlying illnesses develop acute renal failure, and transiently require renal replacement therapy - peritoneal dialysis, intermittent hemodialysis (IHD), or continuous renal replacement therapy (CRRT). As children with acute and chronic renal failure often have multiple comorbid conditions requiring drug therapy, generalists, intensivists, nephrologists, and pharmacists need to be aware of the issues surrounding the management of drug therapy in pediatric patients undergoing renal replacement therapy. This article summarizes the pharmacokinetics and dosing of many drugs commonly prescribed for pediatric patients, and focuses on the management of drug therapy in pediatric patients undergoing IHD and CRRT in the intensive care unit setting. Peritoneal dialysis is not considered in this review. Finally, a summary table with recommended initial dosages for drugs commonly encountered in pediatric patients requiring IHD or CRRT is presented.