Single- and multiple-dose pharmacokinetics and total removal of colistin in a patient with acute kidney injury undergoing extended daily dialysis

Agents of Last Resort: An Update on Polymyxin Resistance

Polymyxin resistance is a major public health threat, because the polymyxins represent last-line therapeutics for gram-negative pathogens resistant to essentially all other antibiotics. Minimizing any potential emergence and dissemination of polymyxin resistance relies on an improved understanding of mechanisms of and risk factors for polymyxin resistance, infection prevention and stewardship strategies, together with optimization of dosing of polymyxins (eg, combination regimens).

Principles of Drug Dosing in Sustained Low Efficiency Dialysis (SLED) and Review of Antimicrobial Dosing Literature

The use of sustained low-efficiency dialysis (SLED) as a renal replacement modality has increased in critically ill patients with both acute kidney injury (AKI) and hemodynamic instability. Unfortunately, there is a paucity of data regarding the appropriate dosing of medications for patients undergoing SLED. Dose adjustment in SLED often requires interpretation of pharmacodynamics and pharmacokinetic factors and extrapolation based on dosing recommendations from other modes of renal replacement therapy (RRT). This review summarizes published trials of antimicrobial dose adjustment in SLED and discusses pharmacokinetic considerations specific to medication dosing in SLED. Preliminary recommendation is provided on selection of appropriate dosing for medications where published literature is unavailable.

International Consensus Guidelines for the Optimal Use of the Polymyxins: Endorsed by the American College of Clinical Pharmacy (ACCP), European Society of Clinical Microbiology and Infectious Diseases (ESCMID), Infectious Diseases Society of America (IDSA), International Society for Anti-infective Pharmacology (ISAP), Society of Critical Care Medicine (SCCM), and Society of Infectious Diseases Pharmacists (SIDP)

The polymyxin antibiotics colistin (polymyxin E) and polymyxin B became available in the 1950s and thus did not undergo contemporary drug development procedures. Their clinical use has recently resurged, assuming an important role as salvage therapy for otherwise untreatable gram-negative infections. Since their reintroduction into the clinic, significant confusion remains due to the existence of several different conventions used to describe doses of the polymyxins, differences in their formulations, outdated product information, and uncertainties about susceptibility testing that has led to lack of clarity on how to optimally utilize and dose colistin and polymyxin B. We report consensus therapeutic guidelines for agent selection and dosing of the polymyxin antibiotics for optimal use in adult patients, as endorsed by the American College of Clinical Pharmacy (ACCP), Infectious Diseases Society of America (IDSA), International Society of Anti-Infective Pharmacology (ISAP), Society for Critical Care Medicine (SCCM), and Society of Infectious Diseases Pharmacists (SIDP). The European Society for Clinical Microbiology and Infectious Diseases (ESCMID) endorses this document as a consensus statement. The overall conclusions in the document are endorsed by the European Committee on Antimicrobial Susceptibility Testing (EUCAST). We established a diverse international expert panel to make therapeutic recommendations regarding the pharmacokinetic and pharmacodynamic properties of the drugs and pharmacokinetic targets, polymyxin agent selection, dosing, dosage adjustment and monitoring of colistin and polymyxin B, use of polymyxin-based combination therapy, intrathecal therapy, inhalation therapy, toxicity, and prevention of renal failure. The treatment guidelines provide the first ever consensus recommendations for colistin and polymyxin B therapy that are intended to guide optimal clinical use.

Pediatric Continuous Renal Replacement Therapy (PCRRT) expert committee recommendation on prescribing prolonged intermittent renal replacement therapy (PIRRT) in critically ill children

INTRODUCTION

Recently, prolonged intermittent renal replacement therapies (PIRRT) have emerged as cost-effective alternatives to conventional CRRT and their use in the pediatric population has started to become more prominent. However, there is a lack of consensus guidelines on the use of PIRRT in pediatric patients in an intensive care setting.

METHODS

A literature search was performed on PubMed/Medline, Embase, and Google Scholar in conjunction with medical librarians from both India and the Cleveland Clinic hospital system to find relevant articles. The Pediatric Continuous Renal Replacement Therapy workgroup analyzed all articles for relevancy, proposed recommendations, and graded each recommendation for their strength of evidence.

RESULTS

Of the 60 studies eligible for review, the workgroup considered data from 37 studies to formulate guidelines for the use of PIRRT in children. The guidelines focused on the definition, indications, machines, and prescription of PIRRT.

CONCLUSION

Although the literature on the use of PIRRT in children is limited, the current studies give credence to their benefits and these expert recommendations are a valuable first step in the continued study of PIRRT in the pediatric population.

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.

A Guide to Understanding Antimicrobial Drug Dosing in Critically Ill Patients on Renal Replacement Therapy

A careful management of antimicrobials is essential in the critically ill with acute kidney injury, especially if renal replacement therapy is required. Acute kidney injury may lead per se to clinically significant modifications of drugs' pharmacokinetic parameters, and the need for renal replacement therapy represents a further variable that should be considered to avoid inappropriate antimicrobial therapy. The most important pharmacokinetic parameters, useful to determine the significance of extracorporeal removal of a given drug, are molecular weight, protein binding, and distribution volume. In many cases, the extracorporeal removal of antimicrobials can be relevant, with a consistent risk of underdosing-related treatment failure and/or potential onset of bacterial resistance. It should also be taken into account that renal replacement therapies are often not standardized in critically ill patients, and their impact on plasma drug concentrations may substantially vary in relation to membrane characteristics, treatment modality, and delivered dialysis dose. Thus, in this clinical scenario, the knowledge of the pharmacokinetic and pharmacodynamic properties of different antimicrobial classes is crucial to tailor maintenance dose and/or time interval according to clinical needs. Finally, especially for antimicrobials known for a tight therapeutic range, therapeutic drug monitoring is strongly suggested to guide dosing adjustment in complex clinical settings, such as septic patients with acute kidney injury undergoing renal replacement therapy.

Clinical Pharmacokinetics, Pharmacodynamics and Toxicodynamics of Polymyxins: Implications for Therapeutic Use

The availability of sensitive, accurate and specific analytical methods for the measurement of polymyxins in biological fluids has enabled an understanding of the pharmacokinetics of these important antibiotics in healthy humans and patients. Colistin is administered as its inactive prodrug colistin methanesulfonate (CMS) and has especially complex pharmacokinetics. CMS undergoes conversion in vivo to the active entity colistin, but the rate of conversion varies from brand to brand and possibly from batch to batch. The extent of conversion is generally quite low and depends on the relative magnitudes of the conversion clearance and other clearance pathways for CMS of which renal excretion is a major component. Formed colistin in the systemic circulation undergoes very extensive tubular reabsorption; the same mechanism operates for polymyxin B which is administered in its active form. The extensive renal tubular reabsorption undoubtedly contributes to the propensity for the polymyxins to cause nephrotoxicity. While there are some aspects of pharmacokinetic behaviour that are similar between the two clinically used polymyxins, there are also substantial differences. In this chapter, the pharmacokinetics of colistin, administered as CMS, and polymyxin B are reviewed, and the therapeutic implications are discussed.

Antibiotic Dosing in Sustained Low-Efficiency Dialysis in Critically Ill Patients

Purpose of review

Sustained low-efficiency dialysis (SLED) is increasingly used as a renal replacement modality in critically ill patients with acute kidney injury (AKI) and hemodynamic instability. There is, therefore, a greater need for the understanding of the antibiotic dosage and pharmacokinetics in these patients, to provide them with optimal therapy.

Sources of information

PubMed/Medline, Embase, and Google Scholar.

Methods

PubMed/Medline, Embase, and Google Scholar databases were searched using a combination of key words: dialysis, end stage renal disease, renal failure, sustained low efficiency dialysis, extended daily dialysis, prolonged intermittent renal replacement therapy (PIRRT), and antibiotic dosing. Studies that investigated antibiotic dosing and pharmacokinetics during SLED/extended daily dialysis/PIRRT were selected for this review.

Key findings

Eleven studies met inclusion criteria and selected for data extraction. The data with regard to dialysis specifications, type of antibiotic including dosages, drug clearances, and dosage recommendations are summarized in Table 1. It is a challenge to find therapeutic doses for antibiotics during SLED therapy because, in general, only aminoglycosides and vancomycin can be assayed in clinical laboratories.

Limitations

Although current studies on antibiotic dosing in SLED are limited due to diverse and undersized patient populations, antibiotic dosage adjustments for patients receiving SLED discussed here will serve as a valuable guide. Future large-scale research should focus on establishing guidelines for antibiotic dosage in SLED.

Implications

Pharmacokinetic principles should be taken into consideration for the appropriate dosing of drugs during SLED, yet it is vital to monitor response to drug to make sure therapeutic goals are achieved. Antibiotic dosing and timing relative to the initiation of SLED may be important to maximize either the time above the minimum inhibitory concentration (MIC) (time-dependent) or the peak to MIC ratio (concentration-dependent), balancing efficacy and toxicity concerns. Critical care physicians should liaise with nephrologists to make decisions regarding appropriate antibiotic dosing in patients undergoing SLED.

Population pharmacokinetics and dosing simulations of ceftazidime in critically ill patients receiving sustained low-efficiency dialysis

Objectives

To describe the population PKs of ceftazidime in critically ill patients receiving sustained low-efficiency dialysis (SLED).

Patients and methods

This study was performed in ICUs of a university hospital. We collected blood samples during three consecutive days of SLED sessions in patients receiving ceftazidime. Concentration versus time curves were analysed using a population PKs approach with Pmetrics ® . Monte Carlo simulation for the first 24 h including a 6 h SLED session was performed with the final model. The fractional target attainment against the MIC of Pseudomonas aeruginosa was executed using targets of 50 and 100% fT  >   MIC .

Results

In total, 211 blood samples of 16 critically ill patients under SLED were collected. SLED treatments were 299.3 (68.4) min in duration. A two-compartment linear population PK model was most appropriate. The mean (SD) CL of ceftazidime on SLED, and off SLED were 5.32 (3.2), 1.06 (1.0) L/h respectively. The PTA for 50% fT  >   MIC for a dose of 1 g intravenously every 8 h was 98%. Assuming a target of 100% fT  >   MIC a dose of 2 g every 12 h covers isolates with MIC ≤8 mg/L with a PTA of 96%.

Conclusion

In critically ill patients receiving SLED, ceftazidime 1 g every 8 h and ceftazidime 2 g every 12 h appear to be sufficient for achieving traditional (50% fT  >   MIC ) and aggressive PD targets (100% fT  >   MIC ) for susceptible isolates (MIC ≤8 mg/L), respectively.

Dosing guidance for intravenous colistin in critically-ill patients

Background

Intravenous colistin is difficult to use because plasma concentrations for antibacterial effect overlap those causing nephrotoxicity, and there is large inter-patient variability in pharmacokinetics. The aim was to develop dosing algorithms for achievement of a clinically desirable average steady-state plasma colistin concentration (C_ss,avg) of 2mg/L.

Methods

Plasma concentration-time data from 214 adult critically-ill patients (creatinine clearance 0-236mL/min; 29 receiving renal replacement therapy (RRT)) were subjected to population pharmacokinetic analysis. Development of an algorithm for patients not receiving RRT was based upon the relationship between the dose of colistimethate that would be needed to achieve a desired C_ss,avg and creatinine clearance. The increase in colistin clearance when patients were on RRT was determined from the population analysis and guided the supplemental dosing needed. To balance potential antibacterial benefit against risk of nephrotoxicity the algorithms were designed to achieve target attainment rates of >80% for C_ss,avg ≥2 and <30% for C_ss,avg ≥4mg/L.

Results

When algorithm doses were applied back to individual patients not on RRT (including patients prescribed intermittent dialysis on a non-dialysis day), >80% of patients with creatinine clearance <80mL/min achieved C_ss,avg ≥2mg/L; but for patients with creatinine clearance ≥80mL/min target attainment was <40%, even with the maximum allowed daily dose of 360mg colistin base activity. For patients receiving RRT, target attainment rates were >80% with the proposed supplemental dosing. In all categories of patients, <30% of patients attained C_ss,avg ≥4mg/L.

Conclusions

The project has generated clinician-friendly dosing algorithms and pointed to circumstances where intravenous monotherapy may be inadequate.

Survey of pharmacists’ antibiotic dosing recommendations for sustained low-efficiency dialysis

BACKGROUND

The use of hybrid renal replacement therapies like sustained low efficiency dialysis (SLED) is increasing in ICUs worldwide. However, pharmacokinetic studies designed to inform therapeutic antibiotic dosing in critically ill patients receiving SLED are limited. SLED operational characteristics vary across institutions. Pharmacists in institutions that utilize SLED are challenged to recommend therapeutic doses for antibiotics.

OBJECTIVE

To characterize pharmacist-recommended antibiotic regimens for SLED.

METHODS

An electronic survey was sent to pharmacist members of the American College of Clinical Pharmacy in the Nephrology or Critical Care Practice and Research Network. Dosing recommendations for a hypothetical critically ill septic patient were collected for cefepime, ceftaroline, daptomycin, levofloxacin, meropenem, and piperacillin/tazobactam. Main outcome measure Antibiotic regimens for the six antibiotics, their frequency, pharmacist’s experience with renal replacement therapies (RRT), post-graduate training, years of clinical experience, number of staffed beds in their hospital, and RRT employed in their ICUs.

RESULTS

The survey was completed by 69 clinical pharmacists who had 8.5 ± 7.5 (mean ± SD) years of experience. All pharmacists had experience dosing medications for patients receiving RRT. The most frequently recommended regimen for each antibiotic was: cefepime 1000 mg every 24 h, ceftaroline 200 mg every 12 h, daptomycin 6 mg/kg every 24 h, levofloxacin 500 mg every 24 h, meropenem 1000 mg every 12 h, and piperacillin/tazobactam 2250 mg every 8 h. Up to nine distinct regimens were recommended for each antibiotic, and the total daily dose between these regimens ranged by as much as a 12-fold. Neither pharmacist’s experience with SLED, post-graduate training, nor years of clinical experience were significantly associated with particular dosing recommendations for the antibiotics.

CONCLUSION

Pharmacists working in institutions that utilize SLED make antibiotic dosing recommendations that vary 4–12-fold depending on the drug. Published research does not provide adequate guidance to optimally dose antibiotics in patients receiving SLED. More SLED pharmacokinetic trials, real-time serum concentration monitoring and advanced pharmacokinetic modeling techniques are necessary to ensure therapeutic dosing in patients receiving SLED.

Colistin Use in Patients With Reduced Kidney Function

Colistin (polymyxin E) is a mainly concentration-dependent bactericidal antimicrobial active against multidrug-resistant Gram-negative bacteria. After being abandoned over the past 30 years due to its neuro- and nephrotoxicity, colistin has been reintroduced recently as a last-resort drug for the treatment of multidrug-resistant Gram-negative bacteria infections in combination with other antimicrobials. Unfortunately, although renal toxicity is a well-known dose-related adverse effect of colistin, relatively few studies are currently available on its peculiar pharmacodynamic/pharmacokinetic properties in clinical settings at high risk for drug accumulation, such as acute or chronic kidney disease. In these specific contexts, the risk for underdosing is also substantial because colistin can be easily removed by dialysis/hemofiltration, especially when the most efficient modalities of renal replacement therapy (RRT) are used in critically ill patients. For this reason, recent recommendations in patients undergoing RRT have shifted toward higher dosing regimens, and therapeutic drug monitoring is advised. This review aims to summarize the main issues related to chemical structure, pharmacodynamics/pharmacokinetics, and renal toxicity of colistin. Moreover, recent data and current recommendations concerning colistin dosing in patients with reduced kidney function, with special regard to those receiving RRT such as dialysis or hemofiltration, are also discussed.

Colistin pharmacokinetics in burn patients during continuous venovenous hemofiltration

While colistin is considered a last resort for the treatment of multidrug-resistant Gram-negative bacterial infections, there has been an increase in its use due to the increasing prevalence of drug-resistant infections worldwide. The pharmacology of colistin is complex, and pharmacokinetic data are limited, especially in patients requiring renal replacement therapy. As a result, dosing for patients who require renal replacement remains a challenge. Here, we present pharmacokinetic data for colistin from two burn patients (37 and 68 years old) infected with colistin-susceptible isoclonal Acinetobacter baumannii and receiving continuous venovenous hemofiltration (CVVH). To our knowledge, we are the first to examine data from before and during CVVH (for one patient), allowing analysis of the effect of CVVH on colistin pharmacokinetics. Pharmacokinetic/pharmacodynamic analysis indicated that a dose increase from 1.5 to 2.2 mg/kg of body weight colistin base activity on CVVH was insufficient to satisfy the target parameter of an AUC24/MIC (area under the concentration-time curve over 24 h in the steady state divided by the MIC) of ≥ 60 at an MIC of ≥ 1 μg/ml in one patient with residual endogenous renal function. Plasma concentrations of colistin ranged from 0 to 15 μg/ml, with free colistin levels ranging from 0.4 to 2.2 μg/ml. While both patients resolved their clinical infections and survived to discharge, colistin-resistant colonizing isolates resulted from therapy in one patient. The variabilities observed in colistin concentrations and pharmacokinetic characteristics highlight the importance of pharmacokinetic monitoring of antibiotics in patients undergoing renal replacement therapy.

Efficient removal of colistin A and B in critically ill patients undergoing CVVHDF and sorbent technologies

BACKGROUND

Colistin pharmacokinetics data are scarce regarding patients undergoing renal replacement therapy (RRT), or even absent as in patients treated with sorbent technologies potentially capable of removing colistin by extensive absorption on many polymeric materials.

METHODS

Twelve septic shock patients with acute kidney injury (AKI) undergoing RRT [continuous venovenous hemodiafiltration (CVVHDF) n = 7, coupled-plasma filtration adsorption-HF (CPFA-HF) n = 4, hemoperfusion n = 1] treated with colistin methanesulfonate at a dose of 4.5 × 10(6) U bid were studied. Colistin A (Col-A) and colistin B (Col-B) concentrations on plasma and effluent at time 0, 0.2, 1, 3, 6, 12, 24 and 48 h were determined by the liquid chromatography-tandem mass spectrometry method.

RESULTS

With CVVHDF the sieving coefficient was lower for Col-A, peaked early (0.40 for Col-A at 10 min, and 0.59 for Col-B at 3 h) and declined after 48 h (0.22 and 0.30 for Col-A and Col-B, respectively). Colistin's filter clearance showed a similar pattern, with the highest clearance value of 18.7 ml/min for Col-B at 1 h. With CPFA-HF after the cartridge the Col-A and Col-B levels were negligible (<0.2 mg/l) or not detectable. The sum of the effluent and cartridge clearances reached values of 30 and 40 ml/min for Col-A and Col-B, respectively. With hemoperfusion the postcartridge concentrations for Col-A and Col-B were about 30 % lower than those determined precartridge.

CONCLUSIONS

During CPFA-HF and CVVHDF, the extent of colistin removal is high, and patients should receive an unreduced dosage. However, due to risk of accumulation in long-term administration colistin plasma levels determination is recommended.