Aminoglycosides in Hemodialysis Patients: Is the Current Practice of Post Dialysis Dosing Appropriate?

Gentamicin Administration in Dialysis Patients: Before or After Hemodialysis?

BACKGROUND

Gentamicin is used to treat severe infections and has a small therapeutic window. This study aimed to optimize the dosing strategy of gentamicin in intermittently hemodialyzed patients by simulating concentration-time profiles during pre- and postdialysis dosing, based on a published pharmacokinetic model.

METHODS

Pharmacokinetic simulations were performed with virtual patients, including septic patients, who were treated with gentamicin and received weekly hemodialysis with an interval of 48 h-48 h-72 h. The following dosing regimens were simulated: for nonseptic patients, 5 mg/kg gentamicin was given 1 h or 2 h before dialysis or a starting dose of 2.5 mg/kg and a maintenance dose of 1.5 mg/kg immediately after dialysis were given; for septic patients, 6 mg/kg gentamicin was given 1 h or 2 h before dialysis or a starting dose of 3 mg/kg and a maintenance dose of 1.8 mg/kg immediately were given after dialysis. The mean maximum concentration (C max ), area under the curve (AUC) 24 h , and target attainment (TA) of pharmacodynamic targets were calculated and compared. The following targets were adopted from the literature: C max >8 mg/L and <20 mg/L and AUC 24 h >70 mg·h/L and <120 mg·h/L.

RESULTS

In nonseptic patients, postdialysis dosing resulted in a TA of 35% for C max of >8 mg/L, 100% for <20 mg/L and AUC 24 h >70 mg·h/L, and 45% for <120 mg·h/L. Dosing 2 h before dialysis resulted in a TA of 100% for C max of >8 mg/L, 40% for <20 mg/L, 65% for AUC 24 h >70 mg·h/L, and 77% for <120 mg·h/L. Simulations of septic patients resulted in comparable outcomes with higher TAs for C max <20 mg/L (96%), AUC 24 h >70 mg·h/L (90%), and AUC 24 h <120 mg·h/L (53%) for dosing 1 h before dialysis.

CONCLUSIONS

Postdialysis dosing resulted in a low TA of C max >8 mg/L; however, predialysis dosing ensured a high TA of C max >8 mg/L and acceptable TA of C max <20 mg/L, AUC 24 h >70 mg·h/L, and AUC 24 h <120 mg·h/L, which could increase the efficacy of gentamicin. Therefore, clinicians should consider predialysis dosing of gentamicin in patients undergoing intermittent hemodialysis.

Therapeutic Drug Monitoring of Antibiotic Drugs in Patients Receiving Continuous Renal Replacement Therapy or Intermittent Hemodialysis: A Critical Review

PURPOSE

Antibiotics are frequently used in patients receiving intermittent or continuous renal replacement therapy (RRT). Continuous renal replacement may alter the pharmacokinetics (PK) and the ability to achieve PK/pharmacodynamic (PD) targets. Therapeutic drug monitoring (TDM) could help evaluate drug exposure and guide antibiotic dosage adjustment. The present review describes recent TDM data on antibiotic exposure and PK/PD target attainment (TA) in patients receiving intermittent or continuous RRT, proposing practical guidelines for performing TDM.

METHODS

Studies on antibiotic TDM performed in patients receiving intermittent or continuous RRT published between 2000 and 2020 were searched and assessed. The authors focused on studies that reported data on PK/PD TA. TDM recommendations were based on clinically relevant PK/PD relationships and previously published guidelines.

RESULTS

In total, 2383 reports were retrieved. After excluding nonrelevant publications, 139 articles were selected. Overall, 107 studies reported PK/PD TA for 24 agents. Data were available for various intermittent and continuous RRT techniques. The study design, TDM practice, and definition of PK/PD targets were inconsistent across studies. Drug exposure and TA rates were highly variable. TDM seems to be necessary to control drug exposure in patients receiving intermittent and continuous RRT techniques, especially for antibiotics with narrow therapeutic margins and in critically ill patients. Practical recommendations can provide insights on relevant PK/PD targets, sampling, and timing of TDM for various antibiotic classes.

CONCLUSIONS

Highly variable antibiotic exposure and TA have been reported in patients receiving intermittent or continuous RRT. TDM for aminoglycosides, beta-lactams, glycopeptides, linezolid, and colistin is recommended in patients receiving RRT and suggested for daptomycin, fluoroquinolones, and tigecycline in critically ill patients on RRT.

Effect of antimicrobials on Stenotrophomonas maltophilia biofilm

Aim: To evaluate the activity of five antimicrobials against young and mature Stenotrophomonas maltophilia biofilms. Materials & methods: Nineteen clinical strains from hemoculture of hemodialysis patients were tested for biofilm kinetics, MIC and minimum biofilm inhibitory concentration (MBIC) in young and mature biofilms. Results: All strains were moderate biofilm producers. MIC showed total susceptibility to levofloxacin and trimethoprim-sulfamethoxazole and partial resistance to ceftazidime (63.2%) and gentamicin (21%). Young and mature biofilms showed the lowest MBIC/MIC ratio for gentamicin, chloramphenicol and levofloxacin, respectively. The highest MBIC/MIC was for trimethoprim-sulfamethoxazole (young) and ceftazidime (mature). Conclusion: Gentamicin displayed surprising activity against S. maltophilia biofilms. Chloramphenicol was indicated as a good option against young S. maltophilia biofilms, and trimethoprim-sulfamethoxazole showed limited antibiofilm activity.

Antibiotic Dosing for Critically Ill Adult Patients Receiving Intermittent Hemodialysis, Prolonged Intermittent Renal Replacement Therapy, and Continuous Renal Replacement Therapy: An Update

Objective: To summarize current antibiotic dosing recommendations in critically ill patients receiving intermittent hemodialysis (IHD), prolonged intermittent renal replacement therapy (PIRRT), and continuous renal replacement therapy (CRRT), including considerations for individualizing therapy. Data Sources: A literature search of PubMed from January 2008 to May 2019 was performed to identify English-language literature in which dosing recommendations were proposed for antibiotics commonly used in critically ill patients receiving IHD, PIRRT, or CRRT. Study Selection and Data Extraction: All pertinent reviews, selected studies, and references were evaluated to ensure appropriateness for inclusion. Data Synthesis: Updated empirical dosing considerations are proposed for antibiotics in critically ill patients receiving IHD, PIRRT, and CRRT with recommendations for individualizing therapy. Relevance to Patient Care and Clinical Practice: This review defines principles for assessing renal function, identifies RRT system properties affecting drug clearance and drug properties affecting clearance during RRT, outlines pharmacokinetic and pharmacodynamic dosing considerations, reviews pertinent updates in the literature, develops updated empirical dosing recommendations, and highlights important factors for individualizing therapy in critically ill patients. Conclusions: Appropriate antimicrobial selection and dosing are vital to improve clinical outcomes. Dosing recommendations should be applied cautiously with efforts to consider local epidemiology and resistance patterns, antibiotic dosing and infusion strategies, renal replacement modalities, patient-specific considerations, severity of illness, residual renal function, comorbidities, and patient response to therapy. Recommendations provided herein are intended to serve as a guide in developing and revising therapy plans individualized to meet a patient's needs.

Gentamicin as Empirical Treatment in Hemodialysis Patients: Safety, Pharmacokinetics, and Pharmacodynamics

The aim of this study was to describe the safety profile and pharmacokinetic/pharmacodynamic parameters in end-stage renal disease patients who received gentamicin as empirical treatment in catheter-related bacteremia when they showed infection signs, regardless of the timing of the next HD. Patients received gentamicin 3 mg/kg before blood culture extraction when they showed infection signs and regardless of the timing of next hemodialysis session. Serum concentrations were collected after the gentamicin administration (peak level) and before the next HD (trough level). Toxicities and adverse drug events were registered. The main pharmacokinetic/pharmacodynamic goal for Gram-negative infections was peak:minimum inhibitory concentration (MIC) ≥10. Sixteen patients were included. Nephrotoxicity was not assessed in this population, and no ototoxicity was found. According to microbial isolation and gentamicin susceptibility, the value of peak:MIC was 5.4 ± 2.0. The administration of gentamicin in these conditions was safe. Estimated pharmacokinetic values were consistent with previous studies and appropriate according to peak:MIC goal for Gram-negative organisms with MIC ≤1 mg/L.

Optimisation of antimicrobial dosing based on pharmacokinetic and pharmacodynamic principles

While suboptimal dosing of antimicrobials has been attributed to poorer clinical outcomes, clinical cure and mortality advantages have been demonstrated when target pharmacokinetic (PK) and pharmacodynamic (PD) indices for various classes of antimicrobials were achieved to maximise antibiotic activity. Dosing optimisation requires a good knowledge of PK/PD principles. This review serves to provide a foundation in PK/PD principles for the commonly prescribed antibiotics (β-lactams, vancomycin, fluoroquinolones and aminoglycosides), as well as dosing considerations in special populations (critically ill and obese patients). PK principles determine whether an appropriate dose of antimicrobial reaches the intended pathogen(s). It involves the fundamental processes of absorption, distribution, metabolism and elimination, and is affected by the antimicrobial's physicochemical properties. Antimicrobial pharmacodynamics define the relationship between the drug concentration and its observed effect on the pathogen. The major indicator of the effect of the antibiotics is the minimum inhibitory concentration. The quantitative relationship between a PK and microbiological parameter is known as a PK/PD index, which describes the relationship between dose administered and the rate and extent of bacterial killing. Improvements in clinical outcomes have been observed when antimicrobial agents are dosed optimally to achieve their respective PK/PD targets. With the rising rates of antimicrobial resistance and a limited drug development pipeline, PK/PD concepts can foster more rational and individualised dosing regimens, improving outcomes while simultaneously limiting the toxicity of antimicrobials.

Optimization of anti-infective dosing regimens during online haemodiafiltration

Online haemodiafiltration (HDF) is increasingly used in clinical practice as a routine intermittent dialysis modality. It is well known that renal impairment and renal replacement therapy can substantially affect the pharmacokinetic behaviour of several drugs. However, surprisingly few data are available on the need for specific dose adjustments during HDF. Due to convection, drug clearance may be increased during HDF as compared with standard haemodialysis. This may be of particular interest in patients undergoing anti-infective therapy, since under-dosing may compromise patient outcomes and promote the emergence of bacterial resistance. Drug clearance during HDF is determined by (i) dialysis characteristics, (ii) drug characteristics and (iii) patient characteristics. In this review, we will discuss these different determinants of drug clearance during HDF and advise on how to adjust the dose of antibacterial, antimycotic and antiviral agents in patients undergoing HDF. In addition, the possible added value of therapeutic drug monitoring is discussed. The review provides guidance for optimization of anti-infective dosing regimens in HDF patients.

Dose Timing of Aminoglycosides in Hemodialysis Patients: A Pharmacology View

Aminoglycosides for patients undergoing intermittent hemodialysis (IHD) have traditionally been dosed at half the normal dose administered at the end of a hemodialysis session. Several investigations have suggested that administering higher doses preceding or with the initiation of dialysis would more readily optimize pharmacodynamic parameters. However, the selection of an optimal aminoglycoside dosing strategy in patients receiving IHD is complex and requires consideration of numerous factors, precluding a singular approach. By reviewing aminoglycoside pharmacokinetics, pharmacodynamics, risks for toxicity and resistance development, and practical considerations, we derive indication- and setting- specific recommendations. We identify some areas (definitive therapy of gram-negative infections in patients receiving predictable hemodialysis sessions, for example) where dosing preceding or with the initiation of dialysis is optimal and feasible, and others (gram-positive synergy, unstable patients with poor/unpredictable vascular access) where postdialysis dosing remains preferred. Finally, given the dearth of data exploring the pharmacodynamics and clinical outcomes of IHD patients receiving aminoglycoside therapy, we identify several key questions in need of investigation.

Gentamicin dosing strategy in patients with end-stage renal disease receiving haemodialysis: evaluation using a semi-mechanistic pharmacokinetic/pharmacodynamic model

OBJECTIVES

Gentamicin is widely used in end-stage renal disease (ESRD) patients for the treatment of infections. The goal of this study was to find the most reasonable dosing regimen for gentamicin in ESRD patients receiving haemodialysis.

METHODS

The in vitro antimicrobial activity of gentamicin was evaluated by static and dynamic time-kill experiments against three bacterial strains of MSSA, MRSA and Pseudomonas aeruginosa. A semi-mechanistic pharmacokinetic/pharmacodynamic (PK/PD) model was established afterwards, allowing the characterization of the antibacterial effect of gentamicin in the human body. The model was utilized to assess dosing regimens of gentamicin in ESRD patients receiving haemodialysis, taking both efficacy and safety into account.

RESULTS

The PK/PD model was capable of describing the bacterial response to gentamicin exposure in all three strains. Simulation based on the PK/PD model showed that pre-dialysis and post-dialysis dosing would bring comparable benefit to the ESRD patient regardless of whether the PK/PD target (fCmax/MIC >8-fold) was achieved, while the post-dialysis dosing resulted in a significantly lower trough concentration. The result of simulated dose fractionation demonstrated that both fCmax/MIC and fAUC(0-24)/MIC are strong predictors of drug effectiveness, but the PK/PD model would provide a more precise prediction of antibacterial activity as well as valuable information on dose selection in ESRD patients receiving haemodialysis.

CONCLUSIONS

Our study supports the original FDA label with regard to the dosing regimen of gentamicin in ESRD patients, which offers adequate clinical benefit as well as an acceptable safety profile.

Gentamicin in hemodialyzed critical care patients: early dialysis after administration of a high dose should be considered

Gentamicin is a widely used antibiotic in the intensive care unit (ICU). Its dosage is difficult to adapt to hemodialyzed ICU patients. The FDA-approved regimen consists of the administration of 1 to 1.7 mg/kg of gentamicin at the end of each dialysis session. Better pharmacokinetic management could be obtained if gentamicin were administered just before the dialysis session. We performed Monte Carlo simulations (MCS) to determine the best gentamicin pharmacokinetic profile (high peak and low trough concentrations). Then, 6 mg/kg of gentamicin was infused into 10 ICU patients over a period of 30 min. A 4-h-long hemodialysis session was started 30 min after the end of the infusion. Pharmacokinetic samples were regularly collected over 24 h. A one-compartment model with zero-order input and first-order elimination was developed in Nonmem version VI to analyze patients' measured gentamicin concentration-versus-time profiles. Finally, additional MCS were performed to compare the regimen chosen with the FDA-approved gentamicin regimen. High peak concentrations (C(max), 31.8 ± 16.8 mg/liter) were achieved. The estimated C(24) and C(48) values (concentrations 24 and 48 h, respectively, after the beginning of the infusion) were 4.1 ± 2.3 and 1.8 ± 1.2 mg/liter, respectively. The volume of distribution was 0.21 ± 0.06 liter/kg. MCS confirmed that the dosing regimen chosen achieved the target C(max) whereas the FDA-approved regimen did not (31.0 ± 10.9 versus 8.8 ± 3.1 mg · liter(-1)). Moreover, the C(24) values were similar while the AUC(0-24) values were moderately increased (190.8 ± 65.0 versus 135 ± 42.2 mg · h · liter(-1)). Therefore, administration of 6 mg/kg of gentamicin before hemodialysis to critically ill patients achieves a high C(max) and an acceptable AUC, maximizing pharmacokinetic/pharmacodynamic endpoints.

N-acetylcysteine use for amelioration of aminoglycoside-induced ototoxicity in dialysis patients

Use of aminoglycoside antibiotics is associated with significant ototoxicity, especially on patients with decreased renal function. The risk of aminoglycoside ototoxicity may approach 60%. Oxidative stress has been suggested as a general mechanism of aminoglycoside ototoxicity and is prevalent in dialysis population. N-acetylcysteine (NAC) is an effective antioxidant and has been safely used in dialysis patients. New experimental and clinical data, explored in this review, provide a good case to recommend NAC administration to all dialysis patients, receiving aminoglycosides.

Clinical Experience with Aminoglycosides in Dialysis-Dependent Patients: Risk Factors for Mortality and Reassessment of Current Dosing Practices

Background::

A resurgence of aminoglycoside use has followed the recent increase of multidrug-resistant gram-negative pathogens and is often needed even in the treatment of dialysis-dependent patients; however, studies evaluating the treatment of gram-negative infections with aminoglycosides, including the optimal dose, in the setting of dialysis are limited.

Objective:

To evaluate the current patterns of aminoglycoside use, including microbiologic and clinical indications, and identify risk factors associated with mortality in dialysis-dependent patients receiving aminoglycosides.

Methods:

Utilization, clinical, and microbiologic data were collected retrospectively over a 2-year period (July 2008-June 2010) for adults with a diagnosis of renal failure requiring dialysis and aminoglycoside therapy. Binary logistic and multivariate regression analyses were performed to identify risk factors for alt-cause 30-day mortality.

Results:

Ninety-five consecutive aminoglycoside courses in 88 patients met inclusion criteria for evaluation. A wide variety of clinical and microbiologic indications were documented. The average duration of aminoglycoside therapy was 5.2 days (range 1-42), the average duration of antimicrobial therapy was 13.5 days (1-60), and the all-cause 30-day mortality rate was 36.5%. Factors associated with all-cause 30-day mortality were gram-negative rod (GNR) bacteremia (OR 28.6; p = 0.035), advanced age (OR 8.5; p = 0.030), recent admission (OR 33.4; p = 0.038). and inadequate empiric therapy (OR 14.9; p = 0.024). Intravenous catheter removal was protective of all-cause 30-day mortality (OR 0.01; p = 0.005). A first pre-dialysis plasma concentration relative to the minimum inhibitory concentration (Cp:MIC) <6 mg/L (gentamicin/tobramycin) was associated with an increased risk of mortality (p = 0.026) upon subgroup analysis of dialysis-dependent patients with GNR bloodstream infections.

Conclusions:

Outcomes among dialysis-dependent patients who received aminoglycosides were below expectations. Various risk factors for mortality were identified, including retention of the catheter, inadequate empiric therapy, and a Cp:MIC <6 mg/L. Improved approaches to dosing of aminoglycosides in dialysis-dependent patients, including more aggressive dosing practices, should be urgently explored in attempts to maximize favorable patient outcomes.

[Level of evidence for therapeutic drug monitoring of aminoglycosides]

Aminoglycosides are major antibiotics indicated for the treatment of infection with gram-negative bacilli. They are characterized by high clinical effectiveness but their main drawback is the occurrence of toxicity in a significant number of patients. Pharmacokinetic parameters of aminoglycosides exhibit wide inter-individual variability and the relationships between concentration and effect have been clearly demonstrated. Consistent studies have demonstrated that therapeutic drug monitoring (TDM) of aminoglycosides administered in multiple daily doses was cost-effective in maximising antibiotic efficacy and/or reducing incidence of toxicity. Therefore TDM of aminoglycosides should be considered "essential". Level of evidence for TDM of aminoglycosides administered once daily is not so clearly demonstrated however it should be highly recommended.

Antibiotic pharmacokinetic and pharmacodynamic considerations in patients with kidney disease

Although pharmacokinetic changes occurring in kidney disease are well described, pharmacodynamics in kidney disease is rarely considered. Knowledge of pharmacodynamic principles can allow a clinician to maximize an antibiotic's effectiveness while minimizing adverse effects and antibacterial resistance. An antibiotic's pharmacokinetic and pharmacodynamic profiles should drive dose adjustment decisions in patients with kidney disease. For example, although the half-lives of beta-lactams and aminoglycosides are both prolonged in these patients, beta-lactams exhibit time-dependent antibacterial activity; consequently, maintenance doses should be smaller but given at the same interval. In contrast, aminoglycosides are concentration-dependent antibiotics; hence prolongation of the dosing interval while using larger doses may be advantageous. The timing of drug administration in relation to hemodialysis may be used to achieve specific pharmacodynamic goals. Aminoglycosides given before hemodialysis generate high peaks, whereas subsequent dialytic drug removal minimizes the area under the serum concentration-time curve, potentially decreasing the risk of developing toxicity. Furthermore, new dialysis prescribing patterns (eg, automated peritoneal dialysis, nocturnal dialysis) affect pharmacokinetic and pharmacodynamic parameters in ways not appreciated by clinicians. Studies quantifying the often considerable drug removal with these therapies, as well as efforts to identify pharmacodynamic targets in patients with kidney disease are essential. This paper reviews pharmacodynamic as well as pharmacokinetic issues that should be considered when prescribing antibiotics to treat infections in this population.