Variability in protein binding of teicoplanin and achievement of therapeutic drug monitoring targets in critically ill patients: lessons from the DALI Study

Necessity for higher teicoplanin doses in older adults: a multicenter prospective observational study in China

BACKGROUND

Many older adult patients receive low-dose teicoplanin with varied regimens, leading to a lack of clarity on its optimal regimens and toxicity profiles in China. This study aimed to clarify these aspects by analyzing teicoplanin treatment concentrations and toxicities.

METHODS

We included older adult patients administered teicoplanin at four tertiary hospitals in Beijing from June 2021 to July 2023, targeting a trough concentration (Cmin) ≥ 10 mg/L. Teicoplanin concentrations and toxicities were monitored dynamically.

RESULTS

From 204 patients, we obtained 632 teicoplanin concentrations. Most patients (83.3%) received low-dose regimens. Suboptimal concentrations were found in 66.4% of patients within 7 days of treatment and 17.0% after 15 days. Cmin gradually increased with treatment duration and was influenced initially by creatinine and by both body weight and creatinine from days 8 to 14. The target concentration was achieved in 53.1%, 33.9%, 15.6%, and 5.5% of patients at 3, ≤ 7, 8-14, and ≥ 15 days after withdrawal, respectively. Slow elimination was associated with average Cmin and eGFR. Nephrotoxicity, hepatotoxicity, and thrombocytopenia occurred in 12.5%, 4.1%, and 31.5% of patients, respectively, without significant differences between concentrations.

CONCLUSIONS

Most older adult patients were underdosed, indicating a need for dose adjustment. Given the varied risk factors for suboptimal concentrations in different treatment stages, a one-size-fits-all regimen was ineffective. We recommend an initial dose of 400 mg at 12-h intervals for the first three days, with subsequent doses from days 4 to 14 adjusted based on creatinine and body weight; after day 14, a maintenance dose of 200 mg daily is advised.

TRIAL REGISTRATION

ChiCTR2100046811; 28/05/2021.

Association of the predicted free blood concentration of teicoplanin with the development of renal dysfunction

PURPOSE

In clinical practice, teicoplanin (TEIC) is typically administered at a trough concentration of 15-40 µg/mL. TEIC has a protein binding rate of approximately 90%, and its concentration rarely exceeds 40 µg/ml. Nevertheless, an increase in the free blood trough concentration may result in renal dysfunction. However, the relationship between the free blood trough concentration and the occurrence of renal dysfunction remains unclear. This study aimed to examine the impact of the predicted free blood concentration on the development of renal dysfunction.

METHODS

This retrospective study included patients who underwent TEIC and had at least one trough concentration measurement. The association between the frequency of renal dysfunction occurrence and the predicted free blood concentration was evaluated using the following equation: free TEIC concentration = total TEIC concentration/(1 + 1.78 × serum albumin level).

RESULTS

Of the 170 patients included in this study, 18% (31/170) developed renal dysfunction. The predicted free trough concentration was significantly higher in the renal dysfunction onset group than in the nononset group. However, the total trough concentration was not significantly associated with the development of renal dysfunction. The odds ratio for developing renal dysfunction was 4.5 (95% confidence interval, 1.9-10.5; P < 0.001) when the predicted free trough concentration was > 4.0 µg/mL.

CONCLUSION

Elevated free trough concentrations of TEIC were associated with an increased risk of renal dysfunction. Controlling the increase in the predicted free blood concentration may effectively prevent the development of renal dysfunction.

Retrospective evaluation of an intervention bundle on OPAT implementation in a large non-university hospital

OBJECTIVES

Optimization of outpatient parenteral antimicrobial therapy (OPAT) requires interdisciplinarity and an operational algorithm. This report retrospectively assesses the impact of a multimodal quality-enhancement intervention bundle on the implementation rate, efficacy, and safety of a home OPAT program in a Belgian large community-based hospital.

METHODS

OPAT recipients between 1 March 2019 and 30 June 2022 were included. The OPAT trajectories were divided into pre-intervention (from 1 March 2019 to 31 October 2020) and post-intervention (from 1 November 2020 to 30 June 2022) groups. The quality-enhancement intervention bundle consisted of the involvement of an infectious disease specialist, revision and implementation of a state-of-the-art prosthetic joint infection diagnosis and treatment protocol, weekly multidisciplinary discussion of all prosthetic joint infections, revision of the OPAT algorithm, and the introduction of teicoplanin as an OPAT-convenient antimicrobial.

RESULTS

Eighty-five patients were included in a total of 96 OPAT trajectories (n = 33 pre-intervention; n = 63 post-intervention). After the intervention, the number of OPAT trajectories nearly doubled. The number of patients with a recurrent infection within 6 months after OPAT completion decreased 15%. The overall 6-month mortality and readmission rates during OPAT treatment decreased 8% and 10%, respectively. Mortality during OPAT treatment did not change. These differences between pre- and post-intervention did not achieve statistical significance, despite the higher risk for complications in the post-intervention group because of increased infection complexity and required treatment duration.

CONCLUSION

Within a Belgian, single, large community-based hospital, a multimodal intervention bundle resulted in increases in OPAT implementation, infection complexity, and required treatment durations without statistically significant differences in outcomes.

Population pharmacokinetics of antibacterial agents in the older population: a literature review

INTRODUCTION

Older individuals face an elevated risk of developing bacterial infections. The optimal use of antibacterial agents in this population is challenging because of age-related physiological alterations, changes in pharmacokinetics (PK) and pharmacodynamics (PD), and the presence of multiple underlying diseases. Therefore, population pharmacokinetics (PPK) studies are of great importance for optimizing individual treatments and prompt identification of potential risk factors.

AREA COVERED

Our search involved keywords such as 'elderly,' 'old people,' and 'geriatric,' combined with 'population pharmacokinetics' and 'antibacterial agents.' This comprehensive search yielded 11 categories encompassing 28 antibacterial drugs, including vancomycin, ceftriaxone, meropenem, and linezolid. Out of 127 studies identified, 26 (20.5%) were associated with vancomycin, 14 (11%) with meropenem, and 14 (11%) with piperacillin. Other antibacterial agents were administered less frequently.

EXPERT OPINION

PPK studies are invaluable for elucidating the characteristics and relevant factors affecting the PK of antibacterial agents in the older population. Further research is warranted to develop and validate PPK models for antibacterial agents in this vulnerable population.

Therapeutic drug monitoring of glycopeptide antimicrobials: An overview of liquid chromatography-tandem mass spectrometry methods

Therapeutic drug monitoring (TDM) is a critical clinical tool used to optimize the safety and effectiveness of drugs by measuring their concentration in biological fluids. These fluids are primarily plasma or blood. TDM, together with real-time dosage adjustment, contributes highly to the successful management of glycopeptide antimicrobial therapies. Understanding pharmacokinetic/pharmacodynamic (PK/PD) properties is vital for optimizing antimicrobial therapies, as the efficacy of these therapies depends on both the exposure of the patient to the drug (PK) and pharmacodynamic (PD) parameters such as the in vitro estimated minimum drug concentration that inhibits bacterial growth (MIC). Liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) is widely recognized as the gold standard for measuring small molecules, such as antibiotics. This review provides a comprehensive overview of LC-MS/MS methods available for TDM of glycopeptide antibiotics, including vancomycin, teicoplanin, dalbavancin, oritavancin, and telavancin.

Population pharmacokinetics and model-based dosing optimization of teicoplanin in elderly critically ill patients with pneumonia

PURPOSE

To evaluate the population pharmacokinetics and pharmacodynamics of teicoplanin in elderly critically ill patients with pneumonia for optimal dosages.

METHODS

Fifteen critically ill patients (9 men) ≥ 60 years received teicoplanin 6 mg/kg for three doses followed by standard maintenance doses (6 mg/kg q24h) with renal dosing adjustment. Serial plasma samples from all patients were analyzed simultaneously by population pharmacokinetic modeling using NONMEM. Probability of target attainment (PTA) was calculated through Monte Carlo simulations for various dosing regimens to achieve adequate systemic exposures.

RESULTS

The median (interquartile range, IQR) age, body mass index, and creatinine clearance (CrCl) was 75 (64-78) years, 22.5 (20.8-25.4) kg/m2, and 64 (47-106) mL/min, respectively. The median (IQR) peak and trough concentration was 46.5 (42.7-51.0) and 8.7 (7.2-9.5) mg/L. The population pharmacokinetic model showed slower clearance (CL) and larger peripheral volume of distribution (V2) in patients with reduced CrCl: CL (L/h) = 0.629 × (CrCl/64)0.656, V2 (L) = 55.7 × (CrCl/64)-0.665. Model-based simulations showed PTAs ≥85% only for higher-dose regimens (12 mg/kg) up to an MIC of 0.5 mg/L.

CONCLUSIONS

Standard teicoplanin dosages for pneumonia may provide inadequate systemic exposures in elderly critically ill patients. High-dose regimens should be considered as empiric therapy or for less susceptible pathogens.

Development and validation of a bioanalytical assay for the measurement of total and unbound teicoplanin in human serum

BACKGROUND

The glycopeptide teicoplanin is considered first-line treatment for severe infections caused by Gram-positive bacteria. Individualized treatment of teicoplanin is gaining interest. As only protein-unbound drug is pharmacologically active, a sensitive assay measuring unbound and total teicoplanin is indispensable for pharmacological research and dose optimization.

OBJECTIVES

To develop and validate a UPLC-MS/MS method to quantify unbound and total teicoplanin in human serum.

METHODS

The developed assay was validated according to the ICH guideline M10 on Bioanalytical Method Validation and study sample analysis. Unbound teicoplanin was obtained by ultrafiltration. The assay was cross-validated with a quantitative microsphere (QMS) immunoassay in a side-by-side comparison using 40 patient samples.

RESULTS

With the developed and validated method, all main teicoplanin components (A2-1, A2-2/A2-3, A2-4/A2-5 and A3-1) can be quantified. Total run time was 5.5 min. Concentration range was 2.5-150 mg/L for total and 0.1-25 mg/L for unbound teicoplanin. Precision (coefficient of variation) and accuracy (bias) of total teicoplanin were 5.97% and 107%, respectively, and 7.17% and 108%, respectively, for unbound teicoplanin.Bland-Altman analysis showed total concentrations measured with the UPLC-MS/MS method were equivalent to the results of the QMS immunoassay. A total of 188 samples from 30 patients admitted to the ICU and haematology department were measured; total concentrations ranged between 2.92 and 98.5 mg/L, and unbound concentrations ranged between 0.37 and 30.7 mg/L.

CONCLUSIONS

The developed method provided rapid, precise and accurate measurement of unbound and total teicoplanin. The developed method is now routinely applied in pharmacological research and clinical practice.

Optimal Teicoplanin Dosage Regimens in Critically Ill Patients: Population Pharmacokinetics and Dosing Simulations Based on Renal Function and Infection Type

Purpose

To develop a population pharmacokinetic model describing teicoplanin concentrations in patients hospitalized in intensive care unit (ICU) and to perform Monte Carlo simulations to provide detailed dosing regimens of teicoplanin.

Methods

This single-center, prospective, observational study was conducted on 151 patients in ICU with 347 plasma samples. The population pharmacokinetics model was established and various covariates were evaluated. The probability of target attainment (PTA) of various proposal dosing regimens was calculated by Monte Carlo simulations.

Results

The two-compartment model adequately described teicoplanin concentration-time data. The estimated glomerular filtration rate (eGFR) associated with systemic clearance (CL) was the only covariate included in the final model. The estimate of CL was 0.838 L/h, with the eGFR adjustment factor of 0.00823. The volume of the central compartment (Vc), inter-compartmental clearance (Q) and volumes of the peripheral compartments (Vp) were 14.4 L, 3.08 L/h and 51.6 L, respectively. The simulations revealed that the standard dosage regimen was only sufficient for the patients with severe renal dysfunction (eGFR ≤ 30 mL/min/1.73 m2) to attain target trough concentration (Cmin, PTA 52.8%). When eGFR > 30 mL/min/1.73 m2, increasing dose and the administration times of loading doses were the preferred options to achieve target Cmin based on the renal function and types of infection.

Conclusion

The most commonly used standard dosage regimen was insufficient for all ICU patients. Our study provided detailed dosing regimens of teicoplanin stratified by eGFR and types of infection for ICU patients.

Therapeutics for Vancomycin-Resistant Enterococcal Bloodstream Infections

Vancomycin-resistant enterococci (VRE) are common causes of bloodstream infections (BSIs) with high morbidity and mortality rates. They are pathogens of global concern with a limited treatment pipeline. Significant challenges exist in the management of VRE BSI, including drug dosing, the emergence of resistance, and the optimal treatment for persistent bacteremia and infective endocarditis. Therapeutic drug monitoring (TDM) for antimicrobial therapy is evolving for VRE-active agents; however, there are significant gaps in the literature for predicting antimicrobial efficacy for VRE BSIs. To date, TDM has the greatest evidence for predicting drug toxicity for the three main VRE-active antimicrobial agents daptomycin, linezolid, and teicoplanin. This article presents an overview of the treatment options for VRE BSIs, the role of antimicrobial dose optimization through TDM in supporting clinical infection management, and challenges and perspectives for the future.

Hypoalbuminemia and Pharmacokinetics: When the Misunderstanding of a Fundamental Concept Leads to Repeated Errors over Decades

Surprisingly, misinterpretation of the influence of hypoalbuminemia on pharmacokinetics and the clinical effects of drugs seems to be a current problem, even though hypoalbuminemia has no impact on the pharmacologically active exposure. Exceptions to this fact are highly protein-bound anaesthetics with high elimination capacity (i.e., <5 drugs on the market). To assess the frequency of misinterpretation of the influence of hypoalbuminemia on pharmacokinetics and the clinical effects of drugs between 1975 and 2021, a PubMed literature review was conducted. Each paragraph on albumin binding was classified as correct, ambiguous or incorrect, creating two acceptable categories: (1) content without any errors, and (2) content containing some incorrect and/or ambiguous statements. The analyses of these articles showed that fewer than 11% of articles contained no interpretation errors. In order to contain this misinterpretation, several measures are proposed: (1) Make the message accessible to a wide audience by offering a simplified and didactic video representation of the lack of impact of albumin binding to drugs. (2) Precise terminology (unbound/free form/concentration) should be used for highly bound drugs. (3) Unbound/free forms should be systematically quantified for highly plasma protein bound drugs for clinical trials as well as for therapeutic drug monitoring.

Population pharmacokinetics and dosing optimization of unbound teicoplanin in Chinese adult patients

Objectives: To develop a population pharmacokinetic (PopPK) model describing unbound teicoplanin concentrations in Chinese adult patients and perform Monte Carlo simulations to optimize the dosing regimens. Methods: The raw data for PopPK analysis in this study were collected from Chinese adult patients. A PopPK model of unbound teicoplanin was developed and Monte Carlo simulations were used to optimize the dosing regimens. The trough concentrations of unbound teicoplanin were targeted at 0.75 mg/L and 1.13 mg/L for most infection induced by Gram-positive bacteria and endocarditis or severe infections, respectively. Results: A total of 103 teicoplanin unbound concentrations were collected from 72 Chinese adult patients. A one-compartment pharmacokinetic model with first-order elimination was established. The typical values of clearance and the volume of distribution were 11.7 L/h and 811 L, respectively. The clearance and volume of distribution of unbound teicoplanin were positively correlated with estimated glomerular filtration rate (eGFR) and serum albumin concentrations, respectively. Dosing simulation results showed that standard dosing regimens were unable to meet the treatment needs of all patients, and the dosing regimen need optimize based on eGFR and serum albumin concentrations. The high eGFR and serum albumin concentration were associated with reduced probability of achieving target unbound trough concentrations. Conclusion: We successfully characterized the pharmacokinetics of unbound teicoplanin in Chinese adult patients. Importantly, we further highlight the importance of guiding dosing through unbound drugs. To achieve safe and effective treatment, the dosing regimens need to be adjusted according to eGFR and serum albumin concentrations.

Comparison of mortality and clinical failure rates between vancomycin and teicoplanin in patients with methicillin-resistant Staphylococcus aureus pneumonia

Background

Very few studies have compared the effects and side effects of vancomycin and teicoplanin in patients with methicillin-resistant Staphylococcus aureus pneumonia. This study aimed to compare the efficacy and safety of vancomycin and teicoplanin in patients with methicillin-resistant Staphylococcus aureus pneumonia.

Methods

This study examined 116 patients with methicillin-resistant Staphylococcus aureus pneumonia who met the inclusion criteria and were treated with either vancomycin (n = 54) or teicoplanin (n = 62). The primary (i.e., clinical failure during treatment) and secondary outcomes (i.e., mortality rates, discontinuation of study drugs due to treatment failure, side effects, and clinical cure) were evaluated.

Results

The vancomycin group presented lower clinical failure rates (25.9% vs. 61.3%, p < 0.001), discontinuation due to treatment failure (22.2% vs. 41.9%, p = 0.024), and mortality rates (3.7% vs 19.4%, p = 0.010). The Cox proportional hazard model revealed that teicoplanin was a significant clinical failure predictor compared with vancomycin (adjusted odds ratio, 2.198; 95% confidence interval 1.163–4.154). The rates of drug change due to side effects were higher in the vancomycin group than in the teicoplanin group (24.1% vs. 1.6%, p < 0.001).

Conclusions

Vancomycin presented favorable treatment outcomes and more side effects compared with teicoplanin, which suggests that clinicians would need to consider the efficacy and potential side effects of these drugs before prescription.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-022-07549-2.

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.

Clinical practice guidelines for therapeutic drug monitoring of teicoplanin: a consensus review by the Japanese Society of Chemotherapy and the Japanese Society of Therapeutic Drug Monitoring

Background

Owing to its low risk of adverse effects, teicoplanin has been extensively used in patients with infections caused by MRSA. To promote the better management of patients receiving teicoplanin, we have updated the guidelines for therapeutic drug monitoring (TDM).

Methods

The guidelines were developed by a committee following the methodology handbook published by the Japanese Medical Information Distribution Service. Nine clinical questions were selected. The committee conducted a systematic review and meta-analysis to establish evidence-based recommendations for the target trough concentration (C_min). An initial electronic database search returned 515 articles, and 97 articles qualified for a full review. Four and five studies were included for the efficacy evaluation of cut-off C_min values of 15 and 20 mg/L, respectively.

Results

Compared with C_min < 15 mg/L, a target C_min value of 15–30 mg/L resulted in increased clinical efficacy in patients with non-complicated MRSA infections (OR = 2.68; 95% CI = 1.14–6.32) without an increase in adverse effects. Although there was insufficient evidence, target C_min values of 20–40 mg/L were suggested in patients with complicated or serious MRSA infections. A 3 day loading regimen followed by maintenance treatment according to renal function was recommended to achieve the target trough concentrations. Because of the prolonged half-life of teicoplanin, measurement of the C_min value on Day 4 before reaching steady state was recommended.

Conclusions

The new guideline recommendations indicate the target C_min value for TDM and the dosage regimen to achieve this concentration and suggest practices for specific subpopulations.

Treatment of MRSA infections in India: Clinical insights from a Delphi analysis

PURPOSE

International and Indian guidelines for the management of patients with methicillin-resistant Staphylococcus aureus (MRSA) infections are available, but the local guidelines are not MRSA-specific. This study aimed to provide clinical insights for the treatment of MRSA infections in India.

METHODS

We used a three-step modified Delphi method to obtain insights. Ten experts comprising infectious disease specialists, microbiologists, pulmonologists, and critical care experts agreed to participate in the analysis. In round 1, a total of 161 statements were circulated to the panel and the experts were asked to 'agree' or 'disagree' by responding 'yes' or 'no' to each statement and provide comments. The same process was used for 73 statements in round 2. Direct interaction with the experts was carried out in round 3 wherein 35 statements were discussed. At least 80% of the experts had to agree for a statement to reach concordance.

RESULTS

Eighty-eight statements in round 1, thirty-eight statements in round 2, and eight statements in round 3 reached concordance and were accepted without modification. The final document comprised 152 statements on the management of various syndromes associated with MRSA such as skin and soft tissue infections, bacteremia and endocarditis, pneumonia, bone and joint infections, and central nervous system infections.

CONCLUSIONS

This analysis will assist clinicians in India to choose an appropriate course of action for MRSA infections.

Enhanced loading dose of teicoplanin for three days is required to achieve a target trough concentration of 20 μg/mL in patients receiving continuous venovenous haemodiafiltration with a low flow rate

INTRODUCTION

Because of its lower risk of renal toxicity than vancomycin, teicoplanin is the preferred treatment for methicillin-resistant Staphylococcus aureus infection in patients undergoing continuous venovenous haemodiafiltration (CVVHDF) in whom renal function is expected to recover. The dosing regimen for achieving a trough concentration (C_min) of ≥20 μg/mL remains unclear in patients on CVVHDF using the low flow rate adopted in Japan.

METHODS

The study was conducted in patients undergoing CVVHDF with a flow rate of <20 mg/kg/h who were treated with teicoplanin. We adopted three loading dose regimens for the initial 3 days: the conventional regimen, a high-dose regimen (four doses of 10 mg/kg), and an enhanced regimen (four doses of 12 mg/kg). The initial C_min was obtained at 72 h after the first dose.

RESULTS

Overall, 60 patients were eligible for study inclusion. The proportion of patients achieving the C_min target was significantly higher for the enhanced regimen than for the high-dose regimen (52.9% versus 8.3%, p = 0.003). In multivariate analysis, the enhanced regimen (odds ratio [OR] = 39.93, 95% confidence interval [CI] = 5.03-317.17) and hypoalbuminaemia (OR = 0.04, 95% CI = 0.01-0.44) were independent predictors of the achievement of C_min ≥ 20 μg/mL.

CONCLUSIONS

An enhanced teicoplanin regimen was proposed to treat complicated or invasive infections by methicillin-resistant Staphylococcus aureus in patients receiving CVVHDF even with a low flow rate.

Pharmacokinetics and Target Attainment of Antibiotics in Critically Ill Children: A Systematic Review of Current Literature

BACKGROUND

Pharmacokinetics (PK) are severely altered in critically ill patients due to changes in volume of distribution (Vd) and/or drug clearance (Cl). This affects the target attainment of antibiotics in critically ill children. We aimed to identify gaps in current knowledge and to compare published PK parameters and target attainment of antibiotics in critically ill children to healthy children and critically ill adults.

METHODS

Systematic literature search in PubMed, EMBASE and Web of Science. Articles were labelled as relevant when they included information on PK of antibiotics in critically ill, non-neonatal, pediatric patients. Extracted PK-parameters included Vd, Cl, (trough) concentrations, AUC, probability of target attainment, and elimination half-life.

RESULTS

50 relevant articles were identified. Studies focusing on vancomycin were most prevalent (17/50). Other studies included data on penicillins, cephalosporins, carbapenems and aminoglycosides, but data on ceftriaxone, ceftazidime, penicillin and metronidazole could not be found. Critically ill children generally show a higher Cl and larger Vd than healthy children and critically ill adults. Reduced target-attainment was described in critically ill children for multiple antibiotics, including amoxicillin, piperacillin, cefotaxime, vancomycin, gentamicin, teicoplanin, amikacin and daptomycin. 38/50 articles included information on both Vd and Cl, but a dosing advice was given in only 22 articles.

CONCLUSION

The majority of studies focus on agents where TDM is applied, while other antibiotics lack data altogether. The larger Vd and higher Cl in critically ill children might warrant a higher dose or extended infusions of antibiotics in this patient population to increase target-attainment. Studies frequently fail to provide a dosing advice for this patient population, even if the necessary information is available. Our study shows gaps in current knowledge and encourages future researchers to provide dosing advice for special populations whenever possible.

Quantification of Teicoplanin Using the HPLC-UV Method for Clinical Applications in Critically Ill Patients in Korea

A high-performance liquid chromatography-ultraviolet detector (HPLC-UV) method has been used to quantify teicoplanin concentrations in human plasma. However, the limited analytical accuracy of previously bioanalytical methods for teicoplanin has given rise to uncertainty due to the use of an external standard. In this study, an internal standard (IS), polymyxin B, was applied to devise a precise, accurate, and feasible HPLC-UV method. The deproteinized plasma sample containing teicoplanin and an IS of acetonitrile was chromatographed on a C18 column with an acidic mobile phase consisting of NaH₂PO₄ buffer and acetonitrile (78:22, v/v) by isocratic elution and detection at 220 nm. The linearity was in the range 7.8–500 mg/L calculated by the ratio of the teicoplanin signal to the IS signal. This analytical method, validated by FDA guidelines with ICH Q2 (R1), was successfully applied to analyze the plasma samples of patients in the intensive care unit for treating serious resistant bacterial infectious diseases, such as those by methicillin-resistant Staphylococcus aureus and Enterococcus faecalis. The methods suggested the potential for use in routine clinical practice for therapeutic drug monitoring of teicoplanin, providing both improved accuracy and a wide range of linearity from lower than steady-state trough concentrations (10 mg/L) to much higher concentrations.

Therapeutic Drug Level Monitoring of Teicoplanin in Korean Pediatric Patients with Normal versus Impaired Renal Function

BACKGROUND

Teicoplanin is used to treat serious gram-positive infections. Optimal teicoplanin trough levels are considered to be ≥ 10 μg/mL. Despite its wide use in various clinical settings, data on teicoplanin trough level in pediatric patients are limited. Therefore, the aim of this study was to investigate the therapeutic drug level monitoring of teicoplanin in Korean pediatric patients, including those with impaired renal function.

METHODS

A retrospective study was performed in pediatric patients (age ≤ 18 years old) who received teicoplanin from September 2014 to April 2018. The regimen included a loading dose of 10 mg/kg/dose at 12 hours' interval three times in a row, and a maintenance dose of 10 mg/kg/dose commenced at 24 hours of interval after the loading dose, with a maximum of 400 mg/dose, respectively. The first therapeutic drug levels were measured. Distribution and characteristics of trough levels in patients with decreased renal function and those with bacteremia were also assessed.

RESULTS

A total of 187 trough levels were collected from 143 patients. Hematologic and oncologic diseases were the most common underlying diseases (83.2%, n = 119). One hundred eighty trough levels were first measured, and their median value was 16.2 μg/mL (range, 2.3-100 μg/mL) and the median interval between initial teicoplanin injection and 1st trough level was 96.5 hours (range 47.6-179.3 hours). Lower steady-state levels were observed in younger age group (median, 13.5 vs. 18.0 μg/mL, P = 0.038). Median trough levels were higher in patients with decreased renal functions (P < 0.001). In addition, among eight with gram-positive bacteremia, seven of them had a favorable outcome.

CONCLUSION

This study provides additive information on trough level monitoring of teicoplanin in children with impaired renal function and treatment effect in patients with gram-positive bacteremia. Careful monitoring for steady state trough levels of teicoplanin is warranted.

Clinical efficacy and safety in patients treated with teicoplanin with a target trough concentration of 20 μg/mL using a regimen of 12 mg/kg for five doses within the initial 3 days

Background

A trough concentration (C_min) ≥20 μg/mL of teicoplanin is recommended for the treatment of serious methicillin-resistant Staphylococcus aureus (MRSA) infections. However, sufficient clinical evidence to support the efficacy of this target C_min has not been obtained. Even though the recommended high C_min of teicoplanin was associated with better clinical outcome, reaching the target concentration is challenging.

Methods

Pharmacokinetics and adverse events were evaluated in all eligible patients. For clinical efficacy, patients who had bacteremia/complicated MRSA infections were analyzed. The primary endpoint for clinical efficacy was an early clinical response at 72–96 h after the start of therapy. Five dosed of 12 mg/kg or 10 mg/kg was administered as an enhanced or conventional high loading dose regimen, respectively. The C_min was obtained at 72 h after the first dose.

Results

Overall, 512 patients were eligible, and 76 patients were analyzed for treatment efficacy. The proportion of patients achieving the target C_min range (20–40 μg/mL) by the enhanced regimen was significantly higher than for the conventional regimen (75.2% versus 41.0%, p < 0.001). In multivariate analysis, C_min ≥ 20 μg/mL was an independent factor for an early clinical response (odds ratio 3.95, 95% confidence interval 1.25–12.53). There was no significant difference in the occurrence of adverse events between patients who did or did not achieve a C_min ≥ 20 μg/mL.

Conclusion

A target C_min ≥ 20 μg/mL might improve early clinical responses during the treatment of difficult MRSA infections using 12 mg/kg teicoplanin for five doses within the initial 3 days.

Antimicrobial therapeutic drug monitoring in critically ill adult patients: a Position Paper

Purpose

This Position Paper aims to review and discuss the available data on therapeutic drug monitoring (TDM) of antibacterials, antifungals and antivirals in critically ill adult patients in the intensive care unit (ICU). This Position Paper also provides a practical guide on how TDM can be applied in routine clinical practice to improve therapeutic outcomes in critically ill adult patients.

Methods

Literature review and analysis were performed by Panel Members nominated by the endorsing organisations, European Society of Intensive Care Medicine (ESICM), Pharmacokinetic/Pharmacodynamic and Critically Ill Patient Study Groups of European Society of Clinical Microbiology and Infectious Diseases (ESCMID), International Association for Therapeutic Drug Monitoring and Clinical Toxicology (IATDMCT) and International Society of Antimicrobial Chemotherapy (ISAC). Panel members made recommendations for whether TDM should be applied clinically for different antimicrobials/classes.

Results

TDM-guided dosing has been shown to be clinically beneficial for aminoglycosides, voriconazole and ribavirin. For most common antibiotics and antifungals in the ICU, a clear therapeutic range has been established, and for these agents, routine TDM in critically ill patients appears meritorious. For the antivirals, research is needed to identify therapeutic targets and determine whether antiviral TDM is indeed meritorious in this patient population. The Panel Members recommend routine TDM to be performed for aminoglycosides, beta-lactam antibiotics, linezolid, teicoplanin, vancomycin and voriconazole in critically ill patients.

Conclusion

Although TDM should be the standard of care for most antimicrobials in every ICU, important barriers need to be addressed before routine TDM can be widely employed worldwide.

Electronic supplementary material

The online version of this article (10.1007/s00134-020-06050-1) contains supplementary material, which is available to authorized users.

How to design a study to evaluate therapeutic drug monitoring in infectious diseases?

BACKGROUND

Therapeutic drug monitoring (TDM) is a tool to personalize and optimize dosing by measuring the drug concentration and subsequently adjusting the dose to reach a target concentration or exposure. The evidence to support TDM is however often ranked as expert opinion. Limitations in study design and sample size have hampered definitive conclusions of the potential added value of TDM.

OBJECTIVES

We aim to give expert opinion and discuss the main points and limitations of available data from antibiotic TDM trials and emphasize key elements for consideration in design of future clinical studies to quantify the benefits of TDM.

SOURCES

The sources were peer-reviewed publications, guidelines and expert opinions from the field of TDM.

CONTENT

This review focuses on key aspects of antimicrobial TDM study design: describing the rationale for a TDM study, assessing the exposure of a drug, assessing susceptibility of pathogens and selecting appropriate clinical endpoints. Moreover we provide guidance on appropriate study design.

IMPLICATIONS

This is an overview of different aspects relevant for the conduct of a TDM study. We believe that this paper will help researchers and clinicians to design and conduct high-quality TDM studies.

Teicoplanin biosynthesis: unraveling the interplay of structural, regulatory, and resistance genes

Teicoplanin (Tcp) is a clinically relevant glycopeptide antibiotic (GPA) that is produced by the actinobacterium Actinoplanes teichomyceticus. Tcp is a front-line therapy for treating severe infections caused by multidrug-resistant Gram-positive pathogens in adults and infants. In this review, we provide a detailed overview of how Tcp is produced by A. teichomyceticus by describing Tcp biosynthesis, regulation, and resistance. We summarize the knowledge gained from in vivo and in vitro studies to provide an integrated model of teicoplanin biosynthesis. Then, we discuss genetic and nutritional factors that contribute to the regulation of teicoplanin biosynthesis, focusing on those that have been successfully applied for improving teicoplanin production. A current view on teicoplanin self-resistance mechanisms in A. teichomyceticus is given, and we compare the Tcp biosynthetic gene cluster with other glycopeptide gene clusters from actinoplanetes and from unidentified isolates/metagenomics samples. Finally, we provide an outlook for further directions in studying Tcp biosynthesis and regulation.

Population pharmacokinetics of total and unbound teicoplanin concentrations and dosing simulations in patients with haematological malignancy

Objectives

To develop a pharmacokinetic model describing total and unbound teicoplanin concentrations in patients with haematological malignancy and to perform Monte Carlo simulations to evaluate target attainment of unbound trough concentrations with various dose regimens.

Methods

This was a hospital-based clinical trial (EudraCT 2013-004535-72). The dosing regimen was 600/800 mg q12h for three doses then 600/800 mg daily. Serial total and unbound teicoplanin concentrations were collected. Maximum protein binding was estimated from serum albumin concentration. Population pharmacokinetic analyses and Monte Carlo simulations were conducted using Pmetrics®. Target total and unbound trough concentrations were ≥20 and ≥1.5 mg/L, respectively.

Results

Thirty adult patients were recruited with a mean (SD) bodyweight of 69.1 (15.8) kg, a mean (SD) CLCR of 72 (41) mL/min and a median (IQR) serum albumin concentration of 29 (4) g/L. A three-compartment complex binding pharmacokinetic model best described the concentration-time data. Total and unbound teicoplanin concentrations were related by serum albumin concentration and a dissociation constant. CLCR and bodyweight were supported as covariates for CL and volume of the central compartment, respectively. Dosing simulations showed that high CLCR was associated with reduced probability of achieving target total and unbound trough concentrations. Low serum albumin concentration was associated with a reduced probability of attaining target total but not unbound trough concentrations. A method to estimate the unbound teicoplanin concentration from the measured total concentration at different serum albumin concentration was demonstrated.

Conclusions

Standard teicoplanin dosing regimens should be used with caution in patients with haematological malignancy. Bodyweight, CLCR and serum albumin concentration are important considerations for appropriate dosing.

Therapeutic drug monitoring of teicoplanin using an LC-MS/MS method: Analysis of 421 measurements in a naturalistic clinical setting

Teicoplanin is a glycopeptide antibiotic used for treatment of severe Gram-positive bacterial infection. The aim of this study was to develop and validate a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for therapeutic drug monitoring (TDM) of teicoplanin and to review our clinical experience. We established an LC-MS/MS method to analyze serum concentration of teicoplanin using simple protein precipitation with a 5 min run time for each sample. The linearity, lower limit of quantitation, detection accuracy, precision, carryover, matrix effect, and extraction recovery were evaluated. From September 2014 to June 2017, a total of 421 serum teicoplanin concentrations was measured in 223 patients. We collected demographic and clinical data, medication history, and laboratory findings through retrospective review of medical records. The LC-MS/MS method was linear for serum teicoplanin concentrations in the range of 12.0-89.0 μg/mL. The intra- and inter-assay precisions were below CV 7.5%. The accuracy was less than ±10% bias. The lower limit of quantification was 0.2 μg/mL. The extraction recovery ranged from 88.8% to 96.6%. Of 421 measurements, 87 (20.7%) were subtherapeutic (< 10 μg/mL), and four (0.9%) were above the toxic threshold (≥ 60 μg/mL). Serum teicoplanin concentration was measured once in 140 patients (63%), and multiple measurements were completed for the others (83 patients, 37%). Intra-patient variability in teicoplanin concentration was found (CV 33%, range 2-94%). Our simple and rapid LC-MS/MS method was successfully applied in TDM of teicoplanin in clinical practice. Such TDM of teicoplanin may be useful for individualized dose adjustment.

New paradigm for rapid achievement of appropriate therapy in special populations: coupling antibiotic dose optimization rapid microbiological methods

INTRODUCTION

Some special patient populations (e.g. critically ill, burns, hematological malignancy, post-major surgery, post-major trauma) have characteristics that lead to higher rates of failure and mortality associated with infection. Choice of effective antibiotics and optimized doses are challenging in these patients that are commonly infected by multidrug-resistant pathogens. Areas covered: A review of the importance of diagnosis and the place of newer microbiological methods (e.g. whole-genome sequencing) to ensure rapid transition from empiric to directed antibiotic therapy is provided. The effects of pathophysiological changes on antibiotic pharmacokinetics are also provided. Expert opinion: Product information dosing regimens do not address the pharmacokinetic alterations that can occur in special patient populations and increase the likelihood of therapeutic failure and the emergence of bacterial resistance. Altered dosing approaches, supplemented with the use of dosing software and therapeutic drug monitoring, may be needed to ensure optimal antibiotic exposure and better therapeutic outcomes in these patients with severe infection. Dose optimization needs to be coupled with advanced microbiological techniques that enable rapid microbiological identification and characterization of resistance mechanism to ensure that maximally effective directed therapy can be chosen.

Old and new glycopeptide antibiotics: From product to gene and back in the post-genomic era

Glycopeptide antibiotics are drugs of last resort for treating severe infections caused by multi-drug resistant Gram-positive pathogens. First-generation glycopeptides (vancomycin and teicoplanin) are produced by soil-dwelling actinomycetes. Second-generation glycopeptides (dalbavancin, oritavancin, and telavancin) are semi-synthetic derivatives of the progenitor natural products. Herein, we cover past and present biotechnological approaches for searching for and producing old and new glycopeptide antibiotics. We review the strategies adopted to increase microbial production (from classical strain improvement to rational genetic engineering), and the recent progress in genome mining, chemoenzymatic derivatization, and combinatorial biosynthesis for expanding glycopeptide chemical diversity and tackling the never-ceasing evolution of antibiotic resistance.

Effect of cardiopulmonary bypass on cytochrome P450 enzyme activity: implications for pharmacotherapy

For patients undergoing cardiopulmonary bypass (CPB) during cardiac surgery, there are well-documented changes in the pharmacokinetics (PK) of commonly administered drugs. Although multiple factors potentially underpin these changes, there has been scant research attention on the impact of CPB to alter the activities of cytochrome P450 (CYP) isoenzymes. PK changes during cardiac surgery with CPB have the potential to adversely affect the safety and efficacy of pharmacotherapy and increase the risk of drug-drug interactions. Clinically significant changes in drug PK during CPB are likely to be prominent for drugs where CYP metabolism is a major clearance (CL) mechanism. However, clinical data from patients undergoing CPB surgery in support of this hypothesis are lacking, leaving a significant knowledge gap. In this review, we address the effects of CPB on the release of pro-inflammatory cytokines, in surgeries with and without CPB, both pre and post initiation of surgery. We reviewed literature to explore the relationship between the release of pro-inflammatory cytokines, and the expression and activities of CYP enzymes. Through this approach, we provide new insight on the effects of CPB on the PK of drugs administered to patients in the clinical setting. Future research to address this knowledge gap will have considerable impact to assist clinicians with optimizing pharmacotherapy in this patient population.

Non-oncotic properties of albumin. A multidisciplinary vision about the implications for critically ill patients

INTRODUCTION

Effective resuscitation with human albumin solutions is achieved with less fluid than with crystalloid solutions. However, the role of albumin in today's critical care unit is also linked to its multiple pharmacological effects. Areas covered: The potential clinical benefits of albumin in select populations of critically ill patients like sepsis seem related to immunomodulatory and anti-inflammatory effects, antibiotic transportation and endothelial stabilization. Albumin transports many drugs used in critically ill patients. Such binding to albumin is frequently lessened in critically ill patients with hypoalbuminemia. These changes could result in sub-optimal treatment. Albumin has immunomodulatory capacity by binding several bacterial products. Albumin also influences vascular integrity, contributing to the maintenance of the normal capillary permeability. Moreover, the albumin molecule encompasses several antioxidant properties, thereby significantly reducing re-oxygenation injury, which is especially important in sepsis. In fact, most studies of albumin administration are a combination of a degree of resuscitation with a degree of maintenance or supplementation of albumin. Expert commentary: The potential clinical benefits of the use of albumin in selected critically ill patients such as sepsis seem related to its immunomodulatory and anti-inflammatory effects, antioxidant properties, antibiotic transportation and endothelial stabilization. Additional studies are warranted to further elucidate the underlying physiologic and molecular rationale.

Right Dose, Right Now: Customized Drug Dosing in the Critically Ill

Drugs are key weapons that clinicians have to battle against the profound pathologies encountered in critically ill patients. Antibiotics in particular are commonly used and can improve patient outcomes dramatically. Despite this, there are strong opportunities for further reducing the persisting poor outcomes for infected critically ill patients. However, taking these next steps for improving patient care requires a new approach to antibiotic therapy. Giving the right dose is highly likely to increase the probability of clinical cure from infection and suppress the emergence of resistant pathogens. Furthermore, in some patients with higher levels of sickness severity, reduced mortality from an optimized approach to antibiotic use could also occur. To enable optimized dosing, the use of customized dosing regimens through either evidence-based dosing nomograms or preferably through the use of dosing software supplemented by therapeutic drug monitoring data should be embedded into daily practice. These customized dosing regimens should also be given as soon as practicable as reduced time to initiation of therapy has been shown to improve patient survival, particularly in the presence of septic shock. However, robust data supporting these logical approaches to therapy, which may deliver the next step change improvement for treatment of infections in critically ill patients, are lacking. Large prospective studies of patient survival and health system costs are now required to determine the value of customized antibiotic dosing, that is, giving the right dose at the right time.

Variability in Trough Total and Unbound Teicoplanin Concentrations and Achievement of Therapeutic Drug Monitoring Targets in Adult Patients with Hematological Malignancy

The objective of this study was to explore the following aspects of teicoplanin use in patients with hematological malignancy: early attainment of target trough concentrations with current high-dose teicoplanin regimens, variability in unbound teicoplanin fractions, factors associated with observed total and unbound trough concentrations, efficacy and toxicity, and renal function estimation. This was a single-center, prospective study. Samples for determination of trough concentrations were taken on days 3, 4, 7, and 10. Total and unbound teicoplanin concentrations were determined using validated high-performance liquid chromatography methods. Regression analyses were used to identify the factors associated with the trough concentration. Thirty teicoplanin-treated adults with hematological malignancy were recruited. Despite the use of dosages higher than the conventional dosages, the proportions of patients with a trough concentration of ≥20 mg/liter at 48 h and at 72 h were 16.7% and 37.9%, respectively. Renal function was significantly negatively associated with total trough concentrations at 48 h and 72 h (P < 0.05). For an average hematological malignancy patient (creatinine clearance = 70 ml/min), sequential loading doses of at least 12 mg/kg of body weight may be needed to achieve early adequate exposure. In the absence of measured creatinine clearance, estimates obtained using the Cockcroft-Gault (total body weight) equation could prove to be an acceptable surrogate. The unbound fractions of teicoplanin were highly variable (3.4 to 18.8%). Higher unbound fractions were observed in patients with low serum albumin concentrations. Teicoplanin was well tolerated. Teicoplanin loading doses higher than those in current use appear to be necessary. Increased dosing is needed in patients with increased renal function. The high variability in protein binding supports the contention for therapeutic drug monitoring of unbound teicoplanin concentrations. (This study has been registered with EudraCT under registration no. 2013-004535-72.).

Population pharmacokinetics of teicoplanin and attainment of pharmacokinetic/pharmacodynamic targets in adult patients with haematological malignancy

OBJECTIVES

To describe the population pharmacokinetics of teicoplanin in adult patients with haematological malignancies receiving higher than standard doses, and to perform Monte Carlo simulations to determine dosing regimens associated with optimal teicoplanin concentrations.

METHODS

This was a hospital-based clinical trial (EudraCT 2013-004535-72). Nine blood samples were collected on Day 3, plus single trough samples on Days 7 and 10, and 24 and 48 hours after the last dose. Teicoplanin minimum inhibitory concentrations were determined for Gram-positive isolates from study patients. Population pharmacokinetic analyses and Monte Carlo dosing simulations were undertaken using Pmetrics.

RESULTS

Thirty adult haematological malignancy patients were recruited with a mean (SD) loading dose, age, total body weight, and creatinine clearance of 9.5 (1.9) mg/kg, 63 (12) years, 69.1 (15.8) kg, and 72 (41) mL/min, respectively. A three-compartment linear pharmacokinetic model best described the teicoplanin concentration data. Covariates supported for inclusion in the final model were creatinine clearance for clearance and total body weight for volume of the central compartment. The median (IQR) area under the concentration-time curve from 48 to 72 hours (AUC_48-72h) was 679 (319) mg.h/L. There was a strong correlation between the AUC_48-72h and trough concentration at 72 hours (Pearson correlation coefficient 0.957, p <0.001). Dosing simulations showed that administration of five loading doses at 12-hourly intervals, stratified by total body weight and creatinine clearance, increased the probability of achieving target concentrations within 72 hours.

CONCLUSIONS

To increase the number of patients achieving optimal teicoplanin concentrations an individualized dosing approach, based on body weight and creatinine clearance, is recommended.

Glycopeptide resistance: Links with inorganic phosphate metabolism and cell envelope stress

Antimicrobial resistance is a critical health issue today. Many pathogens have become resistant to many or all available antibiotics and limited new antibiotics are in the pipeline. Glycopeptides are used as a 'last resort' antibiotic treatment for many bacterial infections, but worryingly, glycopeptide resistance has spread to very important pathogens such as Enterococcus faecium and Staphylococcus aureus. Bacteria confront multiple stresses in their natural environments, including nutritional starvation and the action of cell-wall stressing agents. These stresses impact bacterial susceptibility to different antimicrobials. This article aims to review the links between glycopeptide resistance and different stresses, especially those related with cell-wall biosynthesis and inorganic phosphate metabolism, and to discuss promising alternatives to classical antibiotics to avoid the problem of antimicrobial resistance.

Uncertainty in Antibiotic Dosing in Critically Ill Neonate and Pediatric Patients: Can Microsampling Provide the Answers?

PURPOSE

With a decreasing supply of antibiotics that are effective against the pathogens that cause sepsis, it is critical that we learn to use currently available antibiotics optimally. Pharmacokinetic studies provide an evidence base from which we can optimize antibiotic dosing. However, these studies are challenging in critically ill neonate and pediatric patients due to the small blood volumes and associated risks and burden to the patient from taking blood. We investigate whether microsampling, that is, obtaining a biologic sample of low volume (<50 μL), can improve opportunities to conduct pharmacokinetic studies.

METHODS

We performed a literature search to find relevant articles using the following search terms: sepsis, critically ill, severe infection, intensive care AND antibiotic, pharmacokinetic, p(a)ediatric, neonate. For microsampling, we performed a search using antibiotics AND dried blood spots OR dried plasma spots OR volumetric absorptive microsampling OR solid-phase microextraction OR capillary microsampling OR microsampling. Databases searched include Web of Knowledge, PubMed, and EMbase.

FINDINGS

Of the 32 antibiotic pharmacokinetic studies performed on critically ill neonate or pediatric patients in this review, most of the authors identified changes to the pharmacokinetic properties in their patient group and recommended either further investigations into this patient population or therapeutic drug monitoring to ensure antibiotic doses are suitable. There remain considerable gaps in knowledge regarding the pharmacokinetic properties of antibiotics in critically ill pediatric patients. Implementing microsampling in an antibiotic pharmacokinetic study is contingent on the properties of the antibiotic, the pathophysiology of the patient (and how this can affect the microsample), and the location of the patient. A validation of the sampling technique is required before implementation.

IMPLICATIONS

Current antibiotic regimens for critically ill neonate and pediatric patients are frequently suboptimal due to a poor understanding of altered pharmacokinetic properties. An assessment of the suitability of microsampling for pharmacokinetic studies in neonate and pediatric patients is recommended before wider use. The method of sampling, as well as the method of bioanalysis, also requires validation to ensure the data obtained reflect the true result.

Pharmacokinetic/pharmacodynamic considerations for the optimization of antimicrobial delivery in the critically ill

PURPOSE OF REVIEW

Antimicrobials are very commonly used drugs in the intensive care setting. Extensive research has been conducted in recent years to describe their pharmacokinetics/pharmacodynamics in order to maximize the pharmacological benefit and patient outcome. Translating these new findings into clinical practice is encouraged.

RECENT FINDINGS

This article will discuss mechanistic data on factors causing changes in antimicrobial pharmacokinetics in critically ill patients, such as the phenomena of augmented renal clearance as well as the effects of hypoalbuminemia, renal replacement therapy, and extracorporeal membrane oxygenation. Failure to achieve clinical cure has been correlated with pharmacokinetics/pharmacodynamics target nonattainment, and a recent meta-analysis suggests an association between dosing strategies aimed at optimizing antimicrobial pharmacokinetics/pharmacodynamics with improvement in clinical cure and survival. Novel dosing strategies including therapeutic drug monitoring are also now being tested to address challenges in the optimization of antimicrobial pharmacokinetics/pharmacodynamics.

SUMMARY

Optimization of antimicrobial dosing in accordance with pharmacokinetics/pharmacodynamics targets can improve survival and clinical cure. Dosing regimens for critically ill patients should aim for pharmacokinetics/pharmacodynamics target attainment by utilizing altered dosing strategies including adaptive feedback using therapeutic drug monitoring.

Therapeutic drug monitoring of anti-infective agents in critically ill patients

Initial adequate anti-infective therapy is associated with significantly improved clinical outcomes for patients with severe infections. However, in critically ill patients, several pathophysiological and/or iatrogenic factors may affect the pharmacokinetics of anti-infective agents leading to suboptimal drug exposure, in particular during the early phase of therapy. Therapeutic drug monitoring (TDM) may assist to overcome this problem. We discuss the available evidence on the use of TDM in critically ill patient populations for a number of anti-infective agents, including aminoglycosides, β-lactams, glycopeptides, antifungals and antivirals. Also, we present the available evidence on the practices of anti-infective TDM and describe the potential utility of TDM to improve treatment outcome in critically ill patients with severe infections. For aminoglycosides, glycopeptides and voriconazole, beneficial effects of TDM have been established on both drug effectiveness and potential side effects. However, for other drugs, therapeutic ranges need to be further defined to optimize treatment prescription in this setting.

Measuring unbound versus total vancomycin concentrations in serum and plasma: methodological issues and relevance

BACKGROUND

Studies on the unbound fraction (fu) of vancomycin report highly variable results. Great controversy also exists about the correlation between unbound and total vancomycin concentrations. As differences in (pre-)analytic techniques may explain these findings, we investigated the impact of the procedure used to isolate unbound vancomycin in serum/plasma on fu and the correlation between total and unbound concentrations.

METHODS

Patient samples (n = 39) were analyzed for total and unbound vancomycin concentrations after ultrafiltration (UF, Centrifree at 4°C and 37°C) or equilibrium dialysis (ED, using a Fast Micro-Equilibrium Dialyzer at 37°C) on an Architect i2000SR. To investigate correlations with potential binding proteins, total protein, albumin, alpha-1-acid glycoprotein, and IgA concentrations were also measured.

RESULTS

The median fu after ED was 72.5% [interquartile range (IQR), 68.7%-75.0%]. Ultrafiltration at 4°C and 37°C resulted in a median fu of 51.6% (IQR, 48.6%-54.8%) and 75.2% (IQR, 69.3%-78.6%), respectively, with no significant difference between unbound vancomycin concentrations after ED and UF at 37°C (P = 0.13). Unbound concentrations obtained through ED and UF correlated linearly (4°C: r = 0.9457; 37°C: r = 0.9478; both P < 0.0001). Linear mixed-model regression showed that total vancomycin as such was the predominant determinant for the unbound concentration, allowing a reliable prediction (mean bias ± SD, 5.0% ± 7.6%). The studied protein concentrations were of no added value in predicting the unbound concentration.

CONCLUSIONS

Vancomycin fu after UF at 4°C was on average 30.6% lower than that after UF at 37°C, demonstrating the importance of temperature during UF. Ultrafiltration at 37°C resulted in unbound vancomycin concentrations equivalent with ED. As the unbound concentration could be reliably predicted based on total vancomycin concentrations as such, measurement of unbound vancomycin concentrations has little added value over measurements of total vancomycin concentrations.

Albumin concentration significantly impacts on free teicoplanin plasma concentrations in non-critically ill patients with chronic bone sepsis

The impact of decreased serum albumin concentrations on free antibiotic concentrations in non-critically ill patients is poorly described. This study aimed to describe the pharmacokinetics of a high-dose regimen of teicoplanin, a highly protein-bound antibiotic, in non-critically ill patients with hypoalbuminaemia. Ten patients with chronic bone sepsis and decreased serum albumin concentrations (<35 g/L) receiving teicoplanin 12 mg/kg 12-hourly intravenously for 48 h followed by 12 mg/kg once daily were enrolled. Surgical debridement was performed on Day 3. Samples of venous blood were collected pre-infusion and post-infusion during the first 4 days of therapy. Total and free teicoplanin concentrations were assayed using validated chromatographic methods. The median serum albumin concentration for the cohort was 18 (IQR 15-24) g/L. After 48 h, the median (IQR) free trough (fC(min)) and total trough (tC(min)) concentrations were 2.90 (2.67-3.47) mg/L and 15.54 (10.28-19.12) mg/L, respectively, although trough concentrations declined thereafter. Clearance of the free concentrations was significantly high relative to the total fraction at 38.6 (IQR 29.9-47.8) L/h and 7.0 (IQR 6.8-9.8) L/h, respectively (P<0.001). Multiple linear regression analysis demonstrated that whereas total teicoplanin concentration did not impact on free concentrations (P=0.174), albumin concentration did (P<0.001). This study confirms the significant impact of hypoalbuminaemia on free concentrations of teicoplanin in non-critically ill patients, similar to that in critically ill patients. Furthermore, the poor correlation with total teicoplanin concentration suggests that therapeutic drug monitoring of free concentrations should be used in these patients.

Augmented renal clearance and therapeutic monitoring of β-lactams

Successful application of antibacterial therapy in the critically ill requires an appreciation of the complex interaction between the host, the causative pathogen and the chosen pharmaceutical. A pathophysiological change in the intensive care unit (ICU) patient challenging the 'one dose fits all' concept includes augmented renal clearance (ARC), defined as a creatinine clearance (CL(Cr)) of ≥130 mL/min. Ideally, CL(Cr) values should be obtained by a timed measured collection of urine, with plasma and urine creatinine levels. Increased renal clearance of antibiotics also occurs in the ICU patient and therefore β-lactam antibiotic exposure in the critically ill could easily lead to trough drug concentrations below therapeutic ranges. One way to document and alter drug levels is via therapeutic drug monitoring (TDM). The interactions of ARC and β-lactam TDM are further explored in this article in specific reference to a concomitant article in this issue of the journal.