Micafungin twice-a-week for prophylaxis of invasive Aspergillus infections in children with acute lymphoblastic leukaemia: A controlled cohort study

OBJECTIVES

Invasive Aspergillus infections during the early phase of childhood acute lymphoblastic leukemia (ALL) treatment come with morbidity and mortality. The interaction with vincristine hampers first-line azole prophylaxis. We describe the efficacy of an alternative twice-a-week micafungin regimen for Aspergillus prophylaxis.

METHODS

Newly diagnosed paediatric patients with ALL treated according to the ALL-11 protocol received micafungin twice-a-week (9 mg/kg/dose [max. 300 mg]) during the induction course (first 35 days of treatment) as part of routine care. A historical control cohort without Aspergillus prophylaxis was used. During the first consolidation course (day 36-79), standard itraconazole prophylaxis was used in both groups. The percentage of proven/probable Aspergillus infections during the induction/first consolidation course was compared between the cohorts. The cumulative incidence of proven/probable Aspergillus infections was estimated using a competing risk model. For safety evaluation, liver laboratory chemistry values were analysed.

RESULTS

A total of 169 and 643 paediatric patients with ALL were treated in the micafungin cohort (median age: 4 years [range 1-17]) and historical cohort (median age: 5 years [range 1-17]). The percentage of proven/probable Aspergillus infections was 1·2% (2/169) in the micafungin cohort versus 5·8% (37/643) in the historical cohort (p=0.013; Fisher's exact test). The differences in estimated cumulative incidence were assessed (p=0·014; Gray's test). Although significantly higher ALT/AST values were reported in the micafungin cohort, no clinically relevant side effects were observed.

CONCLUSIONS

Twice-a-week micafungin prophylaxis during the induction course significantly reduced the occurrence of proven/probable Aspergillus infections in the early phase of childhood ALL treatment.

Meta-pharmacokinetic analysis of posaconazole following dosing of oral suspension, delayed-release tablet, and intravenous infusion in patients vs. healthy volunteers: Impact of clinical characteristics and race

OBJECTIVES

To investigate the potential impact of clinical characteristics and the Chinese race on posaconazole pharmacokinetics in patients using an integrated population pharmacokinetic model for posaconazole oral suspension (SUS), delayed-release tablet (DR-tablet), and intravenous (IV) infusion that was developed in healthy volunteers (HV).

METHODS

1046 concentrations from 105 prospectively studied Caucasian patients receiving either of the three posaconazole formulations were pooled with 3898 concentrations from 182 HV. Clinical characteristics were tested for significance. The impact of Chinese race was assessed using 292 opportunistic samples from 80 Chinese patients receiving SUS.

RESULTS

Bioavailability of SUS (Fsus) in patients decreased from 38.2% to 24.6% when the dose was increased from 100 mg to 600 mg. Bioavailability of DR-tablet (Ftab) was 59% regardless of dose. Mucositis, diarrhoea, administration through a nasogastric tube, and concomitant use of proton pump inhibitors or metoclopramide reduced Fsus by 61%, 36%, 44%, 48%, and 29%, respectively, putting patients with these characteristics at increased risk of inadequate exposure. Clearance decreased from 7.0 to 5.1 L/h once albumin levels were <30 g/L. Patients showed an 84.4% larger peripheral volume of distribution (Vp) and 67.5% lower intercompartmental clearance (Q) compared with HV. No racial difference could be identified.

CONCLUSIONS

Pharmacokinetics of posaconazole in patients differ considerably to those in HV, with altered Fsus that is also impacted by clinical covariates, an Ftab similar to fasted conditions in HV, and altered parameters for clearance, Vp, and Q. There was no evidence to indicate that Chinese patients require a different dose to Caucasian patients.

A protocol for an international, multicentre pharmacokinetic study for Screening Antifungal Exposure in Intensive Care Units: The SAFE-ICU study

Objective

To describe whether contemporary dosing of antifungal drugs achieves therapeutic exposures in critically ill patients that are associated with optimal outcomes. Adequate antifungal therapy is a key determinant of survival of critically ill patients with fungal infections. Critical illness can alter an antifungal agents' pharmacokinetics, increasing the risk of inappropriate antifungal exposure that may lead to treatment failure and/or toxicity.

Design setting and participants

This international, multicentre, observational pharmacokinetic study will comprise adult critically ill patients prescribed antifungal agents including fluconazole, voriconazole, posaconazole, isavuconazole, caspofungin, micafungin, anidulafungin, and amphotericin B for the treatment or prophylaxis of invasive fungal disease. A minimum of 12 patients are targeted for enrolment for each antifungal agent, across 12 countries and 30 intensive care units to perform descriptive pharmacokinetics. Pharmacokinetic sampling will occur during two dosing intervals (occasions): firstly, between days 1 and 3, and secondly, between days 4 and 7 of the antifungal course, collecting three samples per occasion. Patients' demographic and clinical data will be collected.

Main outcome measures

The primary endpoint of the study is attainment of pharmacokinetic/pharmacodynamic target exposures that are associated with optimal efficacy. Thirty-day mortality will also be measured.

Results and conclusions

This study will describe whether contemporary antifungal drug dosing achieves drug exposures associated with optimal outcomes. Data will also be used for the development of antifungal dosing algorithms for critically ill patients. Optimised drug dosing should be considered a priority for improving clinical outcomes for critically ill patients with fungal infections.

Therapeutic drug monitoring-guided treatment versus standard dosing of voriconazole for invasive aspergillosis in haematological patients: a multicentre, prospective, cluster randomised, crossover clinical trial

OBJECTIVES

Voriconazole therapeutic drug monitoring (TDM) is recommended based on retrospective data and limited prospective studies. This study aimed to investigate whether TDM-guided voriconazole treatment is superior to standard treatment for invasive aspergillosis.

METHODS

A multicentre (n = 10), prospective, cluster randomised, crossover clinical trial was performed in haematological patients aged ≥18 years treated with voriconazole. All patients received standard voriconazole dose at the start of treatment. Blood/serum/plasma was periodically collected after treatment initiation of voriconazole and repeated during treatment in both groups. The TDM group had measured voriconazole concentrations reported back, with dose adjustments made as appropriate, while the non-TDM group had voriconazole concentrations measured only after study completion. The composite primary endpoint included response to treatment and voriconazole treatment discontinuation due to an adverse drug reaction related to voriconazole within 28 days after treatment initiation.

RESULTS

In total, 189 patients were enrolled in the study. For the composite primary endpoint, 74 patients were included in the non-TDM group and 68 patients in the TDM group. Here, no significant difference was found between both groups (P = 0.678). However, more trough concentrations were found within the generally accepted range of 1-6 mg/L for the TDM group (74.0%) compared with the non-TDM group (64.0%) (P < 0.001).

CONCLUSIONS

In this trial, TDM-guided dosing of voriconazole did not show improved treatment outcome compared with standard dosing. We believe that these findings should open up the discussion for an approach to voriconazole TDM that includes drug exposure, pathogen susceptibility and host defence.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov registration no. NCT00893555.

Liposomal amphotericin B-the past

The discovery of amphotericin B, a polyene antifungal compound, in the 1950s, and the formulation of this compound in a liposomal drug delivery system, has resulted in decades of use in systemic fungal infections. The use of liposomal amphotericin B formulation is referenced in many international guidelines for the treatment of fungal infections such as Aspergillus and cryptococcal disease and Candida infections, as well as other less common infections such as visceral leishmaniasis. With the development of liposomal amphotericin B, an improved therapeutic index could be achieved that allowed the attainment of higher drug concentrations in both the plasma and tissue while simultaneously lowering the toxicity compared with amphotericin B deoxycholate. In over 30 years of experience with this drug, a vast amount of information has been collected on preclinical and clinical efficacy against a wide variety of pathogens, as well as evidence on its toxicity. This article explores the history and nature of the liposomal formulation, the key clinical studies that developed the pharmacokinetic, safety and efficacy profile of the liposomal formulation, and the available microbiological data.

Liposomal amphotericin B exposure in critically ill patients: a prospective pharmacokinetic study

Liposomal amphotericin B (L-AmB) is a broad-spectrum antifungal drug. Little is known about its pharmacokinetics (PK) in critically ill patients. The aim of this study was to document the PK of L-AmB in this population. It was also explored if covariates may be identified that influence its exposure. All adult, critically ill patients (at the intensive care unit or hematology ward) treated with L-AmB between October 2016 and January 2020 were eligible for this study. The administered dose was left at the discretion of the treating clinician. Plasma samples were collected at predose and 1 h, 2 h, 4 h, 8 h, 12 h, 16 h, 20 h and 24 h postdose at an early (day 2-3) and/or later (≥ day 6) treatment day. Additionally, daily trough concentrations were collected until day 14. Thirty-one of 33 included patients were evaluable; their median [IQR] age and body weight was 59 [54-64] years and 68 [59-77] kg, respectively. L-AmB was administered at doses between 2.7 mg/kg and 12.3 mg/kg, with a median [IQR] trough concentration of 3.1 [2.0-4.7] mg/L. The overall median area under the 24h-concentration-time curve (AUC0-24) and peak plasma concentration (Cmax) were 169.0 [117.0-253.0] mg.h/L and 23.2 [16.9-33.7] mg/L, respectively. A considerable intra-and interpatient PK variability for Cmax and AUC0-24 was observed but no explaining variables, except the administered dose, could be identified. The PK of L-AmB in critically ill patients was documented. A considerable variability in exposure was observed between and within patients, however, not associated with a multitude of patient-related characteristics.

Total bodyweight and sex both drive pharmacokinetic variability of fluconazole in obese adults

BACKGROUND

Fluconazole is commonly used to treat or prevent fungal infections. It is typically used orally but in critical situations, IV administration is needed. Obesity may influence the pharmacokinetics and therapeutic efficacy of a drug. In this study, we aim to assess the impact of obesity on fluconazole pharmacokinetics given orally or IV to guide dose adjustments for the obese population.

METHODS

We performed a prospective pharmacokinetic study with intensive sampling in obese subjects undergoing bariatric surgery (n = 17, BMI ≥ 35 kg/m2) and non-obese healthy controls (n = 8, 18.5 ≤ BMI < 30.0 kg/m2). Participants received a semi-simultaneous oral dose of 400 mg fluconazole capsules, followed after 2 h by 400 mg IV. Population pharmacokinetic modelling and simulation were performed using NONMEM 7.3.

RESULTS

A total of 421 fluconazole concentrations in 25 participants (total bodyweight 61.0-174 kg) until 48 h after dosing were obtained. An estimated bioavailability of 87.5% was found for both obese and non-obese subjects, with a 95% distribution interval of 43.9%-98.4%. With increasing total bodyweight, both higher CL and Vd were found. Sex also significantly impacted Vd, being 27% larger in male compared with female participants.

CONCLUSIONS

In our population of obese but otherwise healthy individuals, obesity clearly alters the pharmacokinetics of fluconazole, which puts severely obese adults, particularly if male, at risk of suboptimal exposure, for which adjusted doses are proposed.

Exposure to intravenous posaconazole in critically ill patients with influenza: a pharmacokinetic analysis of the POSA-FLU study

BACKGROUND

Data on posaconazole in the critically ill are scarce. In the POSA-FLU study we examined the prevention of influenza-associated pulmonary aspergillosis with posaconazole in this population.

METHODS

In this observational sub-study, we performed a pharmacokinetic analysis, including protein binding and target attainment (TA). Blood samples were collected over a 24h-dosing interval on both an early (day 2 or 3) and a later (≥ day 4) treatment day.

RESULTS

TA was shown for AUC_0-24 and C_min prophylaxis but not for C_min treatment. Moreover, a saturable protein binding with a significant, positive relationship between albumin concentrations and the maximum binding capacity was observed.

CONCLUSIONS

Our analysis indicates that posaconazole may be a suitable drug to further investigate for prophylaxis, as TA for prophylaxis was reached. Exposure targets for treatment were insufficiently attained in this population.

Optimisation of fluconazole therapy for the treatment of invasive candidiasis in preterm infants

INTRODUCTION

Fluconazole is an important antifungal in the prevention and treatment of invasive Candida infections in neonates, even though its use in preterm infants is still off-label. Here, we performed a population pharmacokinetic study on fluconazole in preterm neonates in order to optimise dosing through the identified predictive patient characteristics.

METHODS

Fluconazole concentrations obtained from preterm infants from two studies were pooled and analysed using NONMEM V.7.3. The developed model was used to evaluate current dosing practice. A therapeutic dosing strategy aiming to reach a minimum target exposure of 400 and 200 mg×hour/L per 24 hours for fluconazole-susceptible C. albicans meningitis and other systemic infections, respectively, was developed.

RESULTS

In 41 preterm neonates with median (range) gestational age 25.3 (24.0-35.1) weeks and median postnatal age (PNA) at treatment initiation 1.4 (0.2-32.5) days, 146 plasma samples were collected. A one-compartment model described the data best, with an estimated clearance of 0.0147 L/hour for a typical infant of 0.87 kg with a serum creatinine concentration of 60 µmol/L and volume of distribution of 0.844 L. Clearance was found to increase with 16% per 100 g increase in actual body weight, and to decrease with 12% per 10 µmol/L increase in creatinine concentration once PNA was above 1 week. Dose adjustments based on serum creatinine and daily dosing are required for therapeutic target attainment.

CONCLUSION

In preterm neonates, fluconazole clearance is best predicted by actual body weight and serum creatinine concentration. Therefore, fluconazole dosing should not only be based on body weight but also on creatinine concentration to achieve optimal exposure in all infants.

ETHICS STATEMENT

The Erasmus MC ethics review board approved the protocol of the DINO Study (MEC-2014-067) and the Radboud UMC ethics review board waived the need for informed consent for cohort 2 (CMO-2021-8302). Written informed consent from parents/legal guardians was obtained prior to study initiation.

Effects of dalteparin on anti-Xa activities cannot be predicted in critically ill COVID-19 patients

Critically ill COVID‐19 patients are at high risk of thromboembolic events despite routine‐dosed low‐molecular‐weight heparin thromboprophylaxis. However, in recent randomized trials increased‐intensity thromboprophylaxis seemed futile and possibly even harmful. In this explorative pharmacokinetic (PK) study we measured anti‐Xa activities on frequent timepoints in 15 critically ill COVID‐19 patients receiving dalteparin and performed PK analysis by nonlinear mixed‐effect modelling. A linear one‐compartment model with first‐order kinetics provided a good fit. However, wide interindividual variation in dalteparin absorption (variance 78%) and clearance (variance 34%) was observed, unexplained by routine clinical covariates. Using the final PK model for Monte Carlo simulations, we predicted increased‐intensity dalteparin to result in anti‐Xa activities well over prophylactic targets (0.2‐0.4 IU/mL) in the majority of patients. Therapeutic‐intensity dalteparin results in supratherapeutic anti‐Xa levels (target 0.6‐1.0 IU/mL) in 19% of patients and subtherapeutic levels in 22%. Therefore, anti‐Xa measurements should guide high‐intensity dalteparin in critically ill COVID‐19 patients.

Pharmacokinetic evaluation of twice-a-week micafungin for prophylaxis of invasive fungal disease in children with acute lymphoblastic leukaemia: a prospective observational cohort study

OBJECTIVES

To determine the pharmacokinetics of twice-a-week micafungin prophylaxis in paediatric leukaemic patients to provide the rationale for this approach.

METHODS

Twice-a-week micafungin at a dose of 9 mg/kg (maximum 300 mg) was given during the leukaemic induction treatment with at least one pharmacokinetic assessment. Non-linear mixed-effects modelling was used for analysis. For model building, our paediatric data were strengthened with existing adult data. Monte Carlo simulations were performed with twice-a-week dosing regimens of 5, 7 and 9 mg/kg and flat dosing per weight band. Simulated paediatric exposures were compared with the exposure in adults after a once-daily 100 mg regimen.

RESULTS

Sixty-one paediatric patients were included with a median age and weight of 4.0 years (range 1.0-17) and 19.5 kg (range 8.60-182), respectively. A two-compartment model best fitted the data. CL and central Vd were lower (P < 0.01) in paediatric patients compared with adults. Predicted exposures (AUC0-168 h) for the 5, 7 and 9 mg/kg and flat dosing per weight band regimens exceeded the adult reference exposure.

CONCLUSIONS

All twice-a-week regimens appeared to result in adequate exposure for Candida therapy, with simulated exposures well above the adult reference exposure. These findings provide the rationale for the pharmacokinetic equivalence of twice-a-week and once-daily micafungin regimens. The greater micafungin exposures seem to be caused by a slower-than-anticipated CL in our paediatric leukaemic patients. The generalizability of our results for Aspergillus prophylaxis cannot be provided without assumptions on target concentrations and within-class identical efficacy.

High unbound flucloxacillin fraction in critically ill patients

Objectives

To describe the unbound and total flucloxacillin pharmacokinetics in critically ill patients and to define optimal dosing strategies.

Patients and methods

Observational multicentre study including a total of 33 adult ICU patients receiving flucloxacillin, given as intermittent or continuous infusion. Pharmacokinetic sampling was performed on two occasions on two different days. Total and unbound flucloxacillin concentrations were measured and analysed using non-linear mixed-effects modelling. Serum albumin was added as covariate on the maximum binding capacity and endogenous creatinine clearance (CL_CR) as covariate for renal function. Monte Carlo simulations were performed to predict the unbound flucloxacillin concentrations for different dosing strategies and different categories of endogenous CL_CR.

Results

The measured unbound concentrations ranged from 0.2 to 110 mg/L and the observed unbound fraction varied between 7.0% and 71.7%. An integral two-compartmental linear pharmacokinetic model based on total and unbound concentrations was developed. A dose of 12 g/24 h was sufficient for 99.9% of the population to achieve a concentration of >2.5 mg/L (100% fT_>5×MIC, MIC = 0.5 mg/L).

Conclusions

Critically ill patients show higher unbound flucloxacillin fractions and concentrations than previously thought. Consequently, the risk of subtherapeutic exposure is low.

Pharmacokinetics and target attainment of intravenous posaconazole in critically ill patients during extracorporeal membrane oxygenation

BACKGROUND

Posaconazole is an antifungal drug used for prophylaxis and treatment of invasive fungal infections. Severe influenza has been identified as a risk factor for invasive pulmonary aspergillosis in critically ill patients. In this population, extracorporeal membrane oxygenation (ECMO) is used as rescue therapy, although little is known about the pharmacokinetics (PK) of posaconazole during ECMO.

OBJECTIVES

To determine the PK and target attainment of six patients treated with IV posaconazole under ECMO and to develop a population PK model that can be used to simulate the PTA.

METHODS

Critically ill patients treated with posaconazole and ECMO were included in this study. Plasma samples were collected at several timepoints within one dosing interval on two occasions: an early (Day 2-3) and a late (Day 4-7) sampling day. Daily trough concentrations were measured.

RESULTS

The median (IQR) AUC0-24, CL and Vd were 34.3 (28.3-37.7) mg·h/L, 8.7 (8.0-10.6) L/h and 389 (314-740) L, if calculated with non-compartmental analysis based on the observed concentrations. All measured trough concentrations were ≥0.7 mg/L and 11/16 were ≥1 mg/L, which are the haematological thresholds for prophylaxis and treatment of invasive aspergillosis, respectively. The targeted PTA (>90%) was attained for prophylaxis but not for treatment.

CONCLUSIONS

ECMO does not appear to influence posaconazole exposure compared with haematology patients. However, some trough levels were below the lower limit for treatment. An a priori dose adjustment does not appear to be necessary but drug monitoring is recommended.

First international quality control programme for laboratories measuring antimicrobial drugs to support dose individualization in critically ill patients

Objectives

International quality control (proficiency testing) programmes are instituted to safeguard the analytical performance of laboratories and to aid these laboratories in identifying sources of error in their analytical methods. We describe the first international quality control programme for antimicrobial agents that are frequently used in critically ill patients.

Methods

Spiked plasma samples with ceftazidime, ciprofloxacin, flucloxacillin, piperacillin, sulfamethoxazole, N-acetyl sulfamethoxazole and trimethoprim were shipped to 22 laboratories from eight different countries. Acceptable accuracy by the performing laboratory was defined if measurements were within 80%–120% limits of the true weighed-in concentrations.

Results

A total of 81% of the measurements (ranging between 56% and 100%, dependent on drug) were within the 80%–120% limits of the true weighed-in concentrations.

Conclusions

We found a relatively good performance of the participating laboratories in measuring eight different antimicrobial drugs. Nevertheless, some of the antimicrobial drugs were not measured properly as up to 44% of the measurements was inaccurate depending on the drug. Our results emphasize the need for and utility of an ongoing quality control programme.

Outpatient parenteral antifungal therapy (OPAT) for invasive fungal infections with intermittent dosing of liposomal amphotericin B

Triazole resistant A. fumigatus has been documented in many parts of the world. In the Netherlands, incidence is now above 10% and results in the need for long-term parenteral therapy with liposomal amphotericin B (LAmB). The long terminal half-life of LAmB suggests that intermittent dosing could be effective, making the application of outpatient antifungal therapy (OPAT) possible. Here, we report our experience with the use of OPAT for Invasive Fungal Infections (IFI). All adult patients treated with LAmB with a 2 or 3 times weekly administration via the outpatient departments in four academic tertiary care centers in the Netherlands and Belgium since January 2010 were included in our analysis. Patient characteristics were collected, as well as information about diagnostics, therapy dose and duration, toxicity, treatment history and outcome of the IFI. In total, 18 patients were included. The most frequently used regimen (67%) was 5 mg/kg 3 times weekly. A partial response to the daily treatment prior to discharge was confirmed by CT-scan in 17 (94%) of patients. A favorable outcome was achieved in 13 (72%) patients. Decrease in renal function occurred in 10 (56%) cases but was reversible in all and was treatment limiting in one patient only. The 100-day mortality and 1-year mortality after initiation of OPAT were 0% and 6%, respectively. In a selected population, and after confirmation of initial response to treatment, our data support the use of OPAT with LAmB for treatment of IFI in an intermittent dosing regimen.

Current Ceftriaxone Dose Recommendations are Adequate for Most Critically Ill Children: Results of a Population Pharmacokinetic Modeling and Simulation Study

Background and Objective

Ceftriaxone is a cornerstone antibiotic for critically ill children with severe infections. Despite its widespread use, information on the pharmacokinetics of ceftriaxone is lacking in this population. We aimed to determine ceftriaxone pharmacokinetics in critically ill children and to propose ceftriaxone dosing guidelines resulting in adequate target attainment using population pharmacokinetic modeling and simulation.

Methods

Critically ill children (aged 0–18 years) treated with intravenous ceftriaxone (100 mg/kg once daily, infused in 30 minutes) and a central or arterial line in place were eligible. Opportunistic blood sampling for total and unbound ceftriaxone concentrations was used. Population pharmacokinetic analysis was performed using non-linear mixed-effects modeling on NONMEM™ Version 7.4.3. Simulations were performed to select optimal doses using probability of target attainment for two pharmacokinetic targets of the minimum inhibitory concentration (MIC) reflecting the susceptibility of pathogens (f T > MIC 100% and fT > 4 × MIC 100%).

Results

Two hundred and five samples for total and 43 time-matched samples for unbound plasma ceftriaxone concentrations were collected from 45 patients, median age 2.5 (range 0.1–16.7) years. A two-compartment model with bodyweight as the co-variate for volume of distribution and clearance, and creatinine-based estimated glomerular filtration rate as an additional covariate for clearance, best described ceftriaxone pharmacokinetics. For a typical patient (2.5 years, 14 kg) with an estimated glomerular filtration rate of 80 mL/min/1.73 m², the current 100-mg/kg once-daily dose results in a probability of target attainment of 96.8% and 60.8% for a MIC of 0.5 mg/L and 4 × MIC (2 mg/L), respectively, when using fT > MIC 100% as a target. For a 50-mg/kg twice-daily regimen, the probability of target attainment was 99.9% and 93.4%, respectively.

Conclusions

The current dosing regimen of ceftriaxone provides adequate exposure for susceptible pathogens in most critically ill children. In patients with an estimated glomerular filtration rate of > 80 mL/min/1.73 m² or in areas with a high prevalence of less-susceptible pathogens (MIC ≥ 0.5 mg/L), a twice-daily dosing regimen of 50 mg/kg can be considered to improve target attainment.

Clinical Trial Registration

POPSICLE study (ClinicalTrials.gov, NCT03248349, registered 14 August, 2017), PERFORM study (ClinicalTrials.gov, NCT03502993, registered 19 April, 2018).

Supplementary Information

The online version contains supplementary material available at 10.1007/s40262-021-01035-9.

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.

Concomitant use of isavuconazole and CYP3A4/5 inducers: Where pharmacogenetics meets pharmacokinetics

BACKGROUND

Isavuconazole is a triazole antifungal drug, approved for the treatment of invasive aspergillosis and mucormycosis. Isavuconazole is metabolised by CYP3A4 and CYP3A5, and it has been shown that the CYP3A inducer rifampin reduces isavuconazole exposure. By extrapolation, the concomitant use of isavuconazole with moderate and strong CYP450 inducers is contraindicated, although it is known that some CYP450 inducers are less potent in comparison with rifampin.

OBJECTIVES

We aim to document exposure to isavuconazole in patients concomitantly treated with a CYP450 inducer that is less potent compared to rifampin. Moreover, although it is well known that CYP3A enzymes are important for the metabolism of isavuconazole, this induction effect has never been studied in combination with the patient's CYP3A genotype.

PATIENTS

We report three patients treated with both isavuconazole and a CYP3A inducer that is less potent compared to rifampin (rifabutin or phenobarbital), in whom we determined isavuconazole concentrations.

RESULTS

These cases suggest that the CYP3A4/5 genotype is an important determinant for isavuconazole exposure and that it might also influence the CYP450 induction interaction.

CONCLUSIONS

CYP3A inducers that are less potent compared to rifampin, may be combined with isavuconazole in patients with loss of CYP3A5 activity (CYP3A5*3/*3). Therapeutic drug monitoring is recommended during this combination. However, low-isavuconazole exposure was observed in the extensive metaboliser with CYP3A4*1/*1 and CYP3A5*1/*3 alleles.

Neuraminidase and SIGLEC15 modulate the host defense against pulmonary aspergillosis

Influenza-associated pulmonary aspergillosis (IAPA) has been reported increasingly since the advent of use of neuraminidase (NA) inhibitors following the 2009 influenza pandemic. We hypothesize that blocking host NA modulates the immune response against Aspergillus fumigatus. We demonstrate that NA influences the host response against A. fumigatus in vitro and that oseltamivir increases the susceptibility of mice to pulmonary aspergillosis. Oseltamivir impairs the mouse splenocyte and human peripheral blood mononuclear cell (PBMC) killing capacity of A. fumigatus, and adding NA restores this defect in PBMCs. Furthermore, the sialic acid-binding receptor SIGLEC15 is upregulated in PBMCs stimulated with A. fumigatus. Silencing of SIGLEC15 decrease PBMC killing of A. fumigatus. We provide evidence that host NA activity and sialic acid recognition are important for anti-Aspergillus defense. NA inhibitors might predispose individuals with severe influenza to invasive aspergillosis. These data shed light on the pathogenesis of invasive fungal infections and may identify potential therapeutic targets.

Clinical Pharmacokinetics of Triazoles in Pediatric Patients

Triazoles represent an important class of antifungal drugs in the prophylaxis and treatment of invasive fungal disease in pediatric patients. Understanding the pharmacokinetics of triazoles in children is crucial to providing optimal care for this vulnerable population. While the pharmacokinetics is extensively studied in adult populations, knowledge on pharmacokinetics of triazoles in children is limited. New data are still emerging despite drugs already going off patent. This review aims to provide readers with the most current knowledge on the pharmacokinetics of the triazoles: fluconazole, itraconazole, voriconazole, posaconazole, and isavuconazole. In addition, factors that have to be taken into account to select the optimal dose are summarized and knowledge gaps are identified that require further research. We hope it will provide clinicians guidance to optimally deploy these drugs in the setting of a life-threatening disease in pediatric patients.

Normal fat mass cannot be reliably estimated in typical pharmacokinetic studies

PURPOSE

An influential covariate for pharmacokinetics is (body) size. Recently, the method of estimation of normal fat mass (NFM) has been advocated. Here, the relative contribution of fat mass, estimated as a fraction fat (Ffat), is used to explain differences in pharmacokinetic parameters. This concept is more and more applied. However, it remains unclear whether NFM can be reliably estimated in these typical studies.

METHODS

We performed an evaluation of the reliability of NFM estimation in a typical study size (n = 30), otherwise best-case scenario, by means of a pharmacokinetic simulation study. Several values of Ffat were investigated.

RESULTS

In a typical pharmacokinetic study, high imprecision was observed for NFM parameter estimates over a range of scenarios. For example, in a scenario where the true value of Ffat on clearance was 0.5, we found a 95% confidence interval of - 0.1 to 2.1, demonstrating a low precision. The implications for practice are that one could conclude that fat-free mass best describes the relationship of the pharmacokinetics with body size, while the true relationship was between fat-free mass and total body weight. Consequently, this could lead to incorrect extrapolation of pharmacokinetics to extreme body sizes.

CONCLUSION

In typical pharmacokinetic studies, NFM should be used with caution because the Ffat estimates have low precision. The estimation of Ffat should always be preceded by careful study design evaluation before planning a study, to ensure that the design and sample size is sufficient to apply this potentially useful methodology.

Ultra-performance liquid chromatography for quantification of amphotericin B plasma concentrations after use of liposomal amphotericin B

OBJECTIVES

Liposomal amphotericin B is widely used to treat life-threatening invasive fungal infections and has replaced conventional amphotericin B deoxycholate due to its more favourable toxicity profile. Despite the fact that liposomal amphotericin B has been licensed for several decades, there is still a paucity of clinical pharmacokinetic data. An assay for the quantification of amphotericin B is necessary to allow the study of its pharmacokinetics.

METHODS

A UPLC-photodiode array (PDA) analytical method was developed and validated (linearity, accuracy, precision, dilution integrity, carry-over, selectivity and stability) in accordance with EMA requirements.

RESULTS

The analytical method was validated over a concentration range of 0.5-50.0 mg/L. Accuracy ranged from 97.6% to 112.1% and within-day repeatability and between-day reproducibility from 1.0% to 6.6% and from 0.4% to 4.6%, respectively, dependent on the concentration. Originally, the goal was to develop an analytical method to separate the liposomal and free amphotericin B fractions, but this was not achieved. Difficulties and bottlenecks encountered are presented.

CONCLUSIONS

A UPLC-PDA analytical method was developed to quantify total amphotericin B in plasma after the use of liposomal amphotericin B.

Nephrotoxicity of concomitant piperacillin/tazobactam and teicoplanin compared with monotherapy

OBJECTIVES

Piperacillin/tazobactam combined with vancomycin has been associated with a decline in renal function when compared with monotherapy. Teicoplanin is a glycopeptide similar to vancomycin. We investigated whether piperacillin/tazobactam combined with teicoplanin is associated with a decline in renal function as well.

METHODS

We conducted a single-centre retrospective cohort study with data from our electronic health records from 9 August 2013 to 15 November 2019, including all adult patients that received either piperacillin/tazobactam, teicoplanin or piperacillin/tazobactam + teicoplanin. The incidence of acute kidney injury (AKI) at 48-72 h served as the primary outcome, whereas change in serum creatinine served as a secondary outcome.

RESULTS

Of the 4202 included patients, 3188 (75.9%) received piperacillin/tazobactam, 791 (18.8%) received teicoplanin and 223 (5.3%) received piperacillin/tazobactam + teicoplanin. The incidence of AKI at 48-72 h after commencement of antibiotic therapy was 5.4% for piperacillin/tazobactam, 3.4% for teicoplanin and 11.7% for piperacillin/tazobactam + teicoplanin (P < 0.001). However, mean serum creatinine at 48-72 h was slightly higher in the piperacillin/tazobactam + teicoplanin group therapy compared with baseline [+1.61% (95% CI -2.25 to 5.70)], indicating a slight decrease in renal function, and decreased for piperacillin/tazobactam [-1.98% (95% CI -2.73 to -1.22)] and teicoplanin [-8.01% (95% CI -9.54 to -6.45)]. After correcting for significant confounders in a multivariate linear regression analysis, these patterns remained.

CONCLUSIONS

Our study suggests that piperacillin/tazobactam + teicoplanin is associated with a higher prevalence of AKI compared with monotherapy. However, as the overall decline in renal function with piperacillin/tazobactam + teicoplanin is very small, its clinical relevance is likely limited. Therefore, piperacillin/tazobactam + teicoplanin can probably be safely combined.

Kallikrein-kinin blockade in patients with COVID-19 to prevent acute respiratory distress syndrome

COVID-19 patients can present with pulmonary edema early in disease. We propose that this is due to a local vascular problem because of activation of bradykinin 1 receptor (B1R) and B2R on endothelial cells in the lungs. SARS-CoV-2 enters the cell via ACE2 that next to its role in RAAS is needed to inactivate des-Arg9 bradykinin, the potent ligand of the B1R. Without ACE2 acting as a guardian to inactivate the ligands of B1R, the lung environment is prone for local vascular leakage leading to angioedema. Here, we hypothesize that a kinin-dependent local lung angioedema via B1R and eventually B2R is an important feature of COVID-19. We propose that blocking the B2R and inhibiting plasma kallikrein activity might have an ameliorating effect on early disease caused by COVID-19 and might prevent acute respiratory distress syndrome (ARDS). In addition, this pathway might indirectly be responsive to anti-inflammatory agents.

The COVID-19 pandemic represents an unprecedented threat to global health. Millions of cases have been confirmed around the world, and hundreds of thousands of people have lost their lives. Common symptoms include a fever and persistent cough and COVID-19 patients also often experience an excess of fluid in the lungs, which makes it difficult to breathe. In some cases, this develops into a life-threatening condition whereby the lungs cannot provide the body's vital organs with enough oxygen.

The SARS-CoV-2 virus, which causes COVID-19, enters the lining of the lungs via an enzyme called the ACE2 receptor, which is present on the outer surface of the lungs’ cells. The related coronavirus that was responsible for the SARS outbreak in the early 2000s also needs the ACE2 receptor to enter the cells of the lungs. In SARS, the levels of ACE2 in the lung decline during the infection.

Studies with mice have previously revealed that a shortage of ACE2 leads to increased levels of a hormone called angiotensin II, which regulates blood pressure. As a result, much attention has turned to the potential link between this hormone system in relation to COVID-19. However, other mouse studies have shown that ACE2 protects against a build-up of fluid in the lungs caused by a different molecule made by the body. This molecule, which is actually a small fragment of a protein, lowers blood pressure and causes fluid to leak out of blood vessels. It belongs to a family of molecules known as kinins, and ACE2 is known to inactivate certain kinins.

This led van de Veerdonk et al. to propose that the excess of fluid in the lungs seen in COVID-19 patients may be because kinins are not being neutralized due to the shortage of the ACE2 receptor. This had not been hypothesized before, even though the mechanism could be the same in SARS which has been researched for the past 17 years. If this hypothesis is correct, it would mean that directly inhibiting the receptor for the kinins (or the proteins that they come from) may be the only way to stop fluid leaking into the lungs of COVID-19 patients in the early stage of disease.

This hypothesis is unproven, and more work is needed to see if it is clinically relevant. If that work provides a proof of concept, it means that existing treatments and registered drugs could potentially help patients with COVID-19, by preventing the need for mechanical ventilation and saving many lives.

Management of cerebral azole-resistant Aspergillus fumigatus infection: A role for intraventricular liposomal-amphotericin B

OBJECTIVES

In the pre-azole era, central nervous system (CNS) infections with Aspergillus had a dismal outcome. Survival improved with voriconazole but CNS infections caused by azole-resistant Aspergillus fumigatus preclude its use. Intravenous liposomal-amphotericin B (L-AmB) is the preferred treatment option for azole-resistant CNS infections but has suboptimal brain concentrations.

METHODS

We describe three patients with biopsy-proven CNS aspergillosis where intraventricular L-AmB was added to systemic therapy. Two patients with azole-resistant aspergillosis and one patient with azole-susceptible CNS aspergillosis were treated with intraventricular L-AmB at a dose of 1mg weekly.

RESULTS

We describe three patients successfully treated with a combination of intravenous and intraventricular L-AmB. All three patients survived but one patient developed serious headaches, most likely not related to this treatment.

CONCLUSIONS

Intraventricular L-AmB may have a role in the treatment of therapy-refractory CNS aspergillosis when added to systemic therapy.

Impact of dose adaptations following voriconazole therapeutic drug monitoring in pediatric patients

Voriconazole is the mainstay of treatment for invasive aspergillosis in immunocompromised pediatric patients. Although Therapeutic Drug Monitoring (TDM) of voriconazole is recommended, it remains unknown if TDM-based dose adaptations result in target attainment. Patients <19 years from two pediatric hematologic-oncology wards were retrospectively identified based on unexplained high voriconazole trough concentrations (Cmin > 6 mg/l). Patient demographics, clinical characteristics, treatment, voriconazole dosing information, voriconazole Cmin before and after adjustment based on TDM were obtained. Twenty-one patients, median (range) age 7.0 (1.2-18.5) years, were identified in two centers. First Cmin (3.1 mg/l [0.1-13.5]) was obtained after 3 days (1-27) of treatment. The median of all Cmin (n = 485, median 11 per patient) was 2.16 mg/l (0.0 (undetectable)-28.0), with 24.1% of Cmin < 1 mg/l, 48.9% 1-4 mg/l, 9.3% 4-6 mg/l, and 17.7% > 6 mg/l. Intrapatient variability was large (94.1% for IV, 88.5% for PO). Dose increases at Cmin < 1 mg/l resulted in an increased Cmin in 76.4%, with 60% between 1 and 4 mg/l. Dose decreases at Cmin > 6 mg/l resulted in a decreased Cmin in 80%, with 51% between 1 and 4 mg/l. Overall, in 45% of the cases (33 out of 55 and 12 out of 45) therapeutic targets were attained after dose adjustment. Fifty-five percent of initial Cmin was outside the therapeutic target of 1-4 mg/l, with multiple dose adaptations required to achieve therapeutic concentrations. Only 60% and 51% of dose adaptations following sub- and supra-therapeutic Cmin, respectively, did result in target attainment. Intensive and continuous TDM of voriconazole is a prerequisite for ensuring adequate exposure in pediatric patients.

European guidelines for primary antifungal prophylaxis in adult haematology patients: summary of the updated recommendations from the European Conference on Infections in Leukaemia

The European Conference on Infections in Leukaemia (ECIL) updated its guidelines on antifungal prophylaxis for adults using the grading system of IDSA. The guidelines were extended to provide recommendations for other haematological diseases besides AML and recipients of an allogeneic haematopoietic stem cell transplantation (HSCT). Posaconazole remains the drug of choice when the incidence of invasive mould diseases exceeds 8%. For patients undergoing remission-induction chemotherapy for AML and myelodysplastic syndrome (MDS), fluconazole can still offer an alternative provided it forms part of an integrated care strategy that includes screening with biomarkers and imaging. Similarly, aerosolized liposomal amphotericin B combined with fluconazole can be considered for patients at high risk of invasive mould diseases but other formulations of the polyene are discouraged. Fluconazole is still recommended as primary prophylaxis for patients at low risk of invasive mould diseases during the pre-engraftment phase of allogeneic HSCT whereas only a moderate recommendation could be made for itraconazole, posaconazole and voriconazole for patients at high risk. Posaconazole is strongly recommended for preventing invasive mould disease post-engraftment but only when graft-versus-host disease (GvHD) was accompanied by other risk factors such as its severity, use of an alternative donor or when unresponsive to standard corticosteroid therapy. The need for primary prophylaxis for other patient groups was less clear and should be defined by the estimated risk of invasive fungal disease (IFD).

Caspofungin dosage adjustments are not required for patients with Child-Pugh B or C cirrhosis

Background

Controversies remain over caspofungin dosage adjustments in cirrhosis, particularly Child-Pugh (CP) B or C. The product information for of caspofungin recommends a maintenance dose reduction from 50 to 35 mg for patients with CP-B cirrhosis.

Objectives

To quantify the impact of cirrhosis and the severity of hepatic impairment on the pharmacokinetics (PK) of caspofungin.

Patients and methods

We performed PK studies of a single 70 mg dose of caspofungin in patients with decompensated CP-B (n = 10) or CP-C (n = 10) cirrhosis and of multiple doses in 21 non-cirrhotic ICU patients with hypoalbuminaemia. A Monte Carlo simulation was performed to investigate the impact of a maintenance dose reduction from 50 to 35 mg on the steady-state area under the 24 h concentration-time curve.

Results

We observed a marginal reduction of caspofungin clearance in a PK study in patients with decompensated CP-B or CP-C cirrhosis. Dose reduction to 35 mg in cirrhotic patients resulted in lower drug exposure than with the approved dose in non-cirrhotic patients.

Conclusions

In contrast to the product information, we recommend giving the full dose of caspofungin regardless of the presence and severity of cirrhosis to avoid a subtherapeutic exposure.

The diagnosis and treatment of invasive aspergillosis in Dutch haematology units facing a rapidly increasing prevalence of azole-resistance. A nationwide survey and rationale for the DB-MSG 002 study protocol

Patients with haematological malignancies are at risk for invasive fungal diseases (IFD). A survey was conducted in all Dutch academic haematology centres on their current diagnostic, prophylactic and therapeutic approach towards IFD in the context of azole-resistance. In all 8 centres, a haematologist and microbiologist filled in the questionnaire that focused on different subgroups of haematology patients. Fungal prophylaxis during neutropaenia was directed against Candida and consisted of fluconazole and/or amphotericin B suspension. Mould-active prophylaxis was given to acute myeloid leukaemia patients during chemotherapy in 2 of 8 centres. All centres used azole prophylaxis in a subset of patients with graft-versus-host disease. A uniform approach towards the diagnosis and treatment of IFD and in particular azole-resistant Aspergillus fumigatus was lacking. In 2017, all centres agreed to implement a uniform diagnostic and treatment algorithm regarding invasive aspergillosis with a central role for comprehensive diagnostics and PCR-based detection of azole-resistance. This study (DB-MSG 002) will re-evaluate this algorithm when 280 patients have been treated. A heterogeneous approach towards antifungal prophylaxis, diagnosis and treatment was apparent in the Netherlands. Facing triazole-resistance, consensus was reached on the implementation of a uniform diagnostic approach in all 8 centres.

Caspofungin Population Pharmacokinetics in Critically Ill Patients Undergoing Continuous Veno-Venous Haemofiltration or Haemodiafiltration

BACKGROUND AND OBJECTIVE

Sepsis and continuous renal replacement therapy (CRRT) can both significantly affect antifungal pharmacokinetics. This study aimed to describe the pharmacokinetics of caspofungin in critically ill patients during different CRRT modes.

METHODS

Patients receiving caspofungin and undergoing continuous veno-venous haemofiltration (CVVH) or haemodiafiltration (CVVHDF) were eligible to take part in the study. Blood samples were collected at seven sampling times during a dosing interval. Demographics and clinical data were recorded. Population pharmacokinetic analysis and Monte-Carlo simulation were undertaken using Pmetrics.

RESULTS

Twelve pharmacokinetic profiles from nine patients were analysed. The caspofungin CRRT clearance (CL) was 0.048 ± 0.12 L/h for CVVH and 0.042 ± 0.042 L/h for CVVHDF. A two-compartment linear model best described the data. Patient weight was the only covariate affecting drug CL and central volume. The mean (standard deviation) parameter estimates were 0.64 ± 0.12 L/h for CL, 9.35 ± 3.56 L for central volume, 0.25 ± 0.19 per h for the rate constant for drug distribution from central to peripheral compartments and 0.19 ± 0.10 per h from peripheral to central compartments. Based on simulation results, a caspofungin 100 mg loading dose followed by a 50 mg maintenance dose for patients with a total body weight of ≤80 kg best achieved the pharmacokinetic/PD targets whilst a 70 mg maintenance dose was required for patients with a weight of >80 kg.

CONCLUSION

No caspofungin dosing adjustment is necessary for patients undergoing either form of CRRT. However, higher than recommended loading doses of caspofungin are required to achieve pharmacokinetic/pharmacodynamic targets in critically ill patients. Registration: ClinicalTrials.gov Identifier NCT01403220.

Pharmacokinetics of Anidulafungin in Obese and Normal-Weight Adults

In 2025, approximately one out of five adults will be obese. Physiological changes associated with obesity have been shown to influence the pharmacokinetics of drugs. Anidulafungin is frequently used in critically ill patients, and to achieve optimal efficacy, it is essential that its dose is appropriate for each patient's characteristics. We combined data from obese subjects with data from normal-weight subjects and determined an optimal dosing regimen for obese patients by population pharmacokinetic modeling. Twenty adults, 12 of which were normal-weight healthy subjects (median weight, 67.7 kg; range, 61.5 to 93.6 kg) and 8 of which were morbidly obese subjects (median weight, 149.7 kg; range, 124.1 to 166.5 kg) were included in the analysis. Subjects received a single dose of 100 mg anidulafungin intravenously over 90 min, upon which blood samples were obtained. Monte Carlo simulations were performed to optimize dosing in obesity. A three-compartment model and equal volumes of distribution described the data best. Total body weight was identified as a descriptor for both clearance and the volume of distribution, but the effect of weight on these parameters was limited. Simulations showed that with the licensed 100-mg dose, more than 97% of subjects with a weight above 140 kg will have an area under the concentration-time curve from 0 to 24 h of less than 99 mg · h/liter (the reference value for normal-weight individuals). We found that in obese and normal-weight subjects, weight influenced both of the anidulafungin pharmacokinetic parameters clearance and volume of distribution, implying a lower exposure to anidulafungin in (morbidly) obese individuals. Consequently, a 25% increase in the loading and maintenance doses could be considered in patients weighing more than 140 kg.

Cancer prevention by aspirin in children with Constitutional Mismatch Repair Deficiency (CMMRD)

Constitutional MisMatch Repair Deficiency (CMMRD) is caused by homozygous or compound heterozygous germline variants in one of the mismatch repair (MMR) genes (MSH2, MSH6, PMS2, MLH1). This syndrome results in early onset colorectal cancer, leukemia and lymphoma, brain tumors and other malignancies. Children with CMMRD are at high risk of developing multiple cancers and cancer surveillance does not guarantee detection of cancer at a curable stage. The development of a preventive treatment strategy would be a major step forward. Long-term daily use of acetylsalicylic acid (ASA) has been shown to reduce cancer risk in individuals with Lynch syndrome (LS). LS is caused by heterozygous germline variants of MSH2, MSH6, PMS2 and MLH1 and characterized by an increased risk of developing colorectal and endometrial cancer at adult age. Here we discuss the potential use of ASA for cancer prevention in patients with CMMRD.

Population Pharmacokinetic Model and Pharmacokinetic Target Attainment of Micafungin in Intensive Care Unit Patients

OBJECTIVE

To study the pharmacokinetics of micafungin in intensive care patients and assess pharmacokinetic (PK) target attainment for various dosing strategies.

METHODS

Micafungin PK data from 20 intensive care unit patients were available. A population-PK model was developed. Various dosing regimens were simulated: licensed regimens (I) 100 mg daily; (II) 100 mg daily with 200 mg from day 5; and adapted regimens 200 mg on day 1 followed by (III) 100 mg daily; (IV) 150 mg daily; and (V) 200 mg daily. Target attainment based on a clinical PK target for Candida as well as non-Candida parapsilosis infections was assessed for relevant minimum inhibitory concentrations [MICs] (Clinical and Laboratory Standards Institute). Parameter uncertainty was taken into account in simulations.

RESULTS

A two-compartment model best fitted the data. Clearance was 1.10 (root square error 8%) L/h and V 1 and V 2 were 17.6 (root square error 14%) and 3.63 (root square error 8%) L, respectively. Median area under the concentration-time curve over 24 h (interquartile range) on day 14 for regimens I-V were 91 (67-122), 183 (135-244), 91 (67-122), 137 (101-183) and 183 (135-244) mg h/L, respectively, for a typical patient of 70 kg. For the MIC/area under the concentration-time curve >3000 target (all Candida spp.), PK target attainment was >91% on day 14 (MIC 0.016 mg/L epidemiological cut-off) for all of the dosing regimens but decreased to (I) 44%, (II) 91%, (III) 44%, (IV) 78% and (V) 91% for MIC 0.032 mg/L. For the MIC/area under the concentration-time curve >5000 target (non-C. parapsilosis spp.), PK target attainment varied between 62 and 96% on day 14 for MIC 0.016.

CONCLUSIONS

The licensed micafungin maintenance dose results in adequate exposure based on our simulations with a clinical PK target for Candida infections but only 62% of patients reach the target for non-C. parapsilosis. In the case of pathogens with an attenuated micafungin MIC, patients may benefit from dose escalation to 200 mg daily. This encourages future study.

The role of the multidisciplinary team in antifungal stewardship

There are a variety of challenges faced in the management of invasive fungal diseases (IFD), including high case-fatality rates, high cost of antifungal drugs and development of antifungal resistance. The diagnostic challenges and poor outcomes associated with IFD have resulted in excessive empirical use of antifungals in various hospital settings, exposing many patients without IFD to potential drug toxicities as well as causing spiralling antifungal drug costs. Further complexity arises as different patient groups show marked variation in their risk for IFD, fungal epidemiology, sensitivity and specificity of diagnostic tests and the pharmacokinetics and pharmacodynamics of antifungal drugs. To address these issues and to ensure optimal management of IFD, specialist knowledge and experience from a range of backgrounds is required, which extends beyond the remit of most antibiotic stewardship programmes. The first step in the development of any antifungal stewardship (AFS) programme is to build a multidisciplinary team encompassing the necessary expertise in the management of IFD to develop and implement the AFS programme. The specific roles of the key individuals within the AFS team and the importance of collaboration are discussed in this article.

The role of infection models and PK/PD modelling for optimising care of critically ill patients with severe infections

Critically ill patients with severe infections are at high risk of suboptimal antimicrobial dosing. The pharmacokinetics (PK) and pharmacodynamics (PD) of antimicrobials in these patients differ significantly from the patient groups from whose data the conventional dosing regimens were developed. Use of such regimens often results in inadequate antimicrobial concentrations at the site of infection and is associated with poor patient outcomes. In this article, we describe the potential of in vitro and in vivo infection models, clinical pharmacokinetic data and pharmacokinetic/pharmacodynamic models to guide the design of more effective antimicrobial dosing regimens. Individualised dosing, based on population PK models and patient factors (e.g. renal function and weight) known to influence antimicrobial PK, increases the probability of achieving therapeutic drug exposures while at the same time avoiding toxic concentrations. When therapeutic drug monitoring (TDM) is applied, early dose adaptation to the needs of the individual patient is possible. TDM is likely to be of particular importance for infected critically ill patients, where profound PK changes are present and prompt appropriate antibiotic therapy is crucial. In the light of the continued high mortality rates in critically ill patients with severe infections, a paradigm shift to refined dosing strategies for antimicrobials is warranted to enhance the probability of achieving drug concentrations that increase the likelihood of clinical success.

Altered Micafungin Pharmacokinetics in Intensive Care Unit Patients

Micafungin is considered an important agent for the treatment of invasive fungal infections in the intensive care unit (ICU). Little is known on the pharmacokinetics of micafungin. We investigated micafungin pharmacokinetics (PK) in ICU patients and set out to explore the parameters that influence micafungin plasma concentrations. ICU patients receiving 100 mg of intravenous micafungin once daily for suspected or proven fungal infection or as prophylaxis were eligible. Daily trough concentrations and PK curves (days 3 and 7) were collected. Pharmacokinetic analysis was performed using a standard two-stage approach. Twenty patients from the ICUs of four hospitals were evaluated. On day 3 (n = 20), the median (interquartile range [IQR]) area under the concentration-time curve from 0 to 24 h (AUC0-24) was 78.6 (65.3 to 94.1) mg · h/liter, the maximum concentration of drug in serum (Cmax) was 7.2 (5.4 to 9.2) mg/liter, the concentration 24 h after dosing (C24) was 1.55 (1.4 to 3.1) mg/liter, the volume of distribution (V) was 25.6 (21.3 to 29.1) liters, the clearance (CL) was 1.3 (1.1 to 1.5) liters/h, and the elimination half-life (t1/2) was 13.7 (12.2 to 15.5) h. The pharmacokinetic parameters on day 7 (n = 12) were not significantly different from those on day 3. Daily trough concentrations (day 3 to the end of therapy) showed moderate interindividual (57.9%) and limited intraindividual variability (12.9%). No covariates of the influence on micafungin exposure were identified. Micafungin was considered safe and well tolerated. We performed the first PK study with very intensive sampling on multiple occasions in ICU patients, which aided in resolving micafungin PK. Strikingly, micafungin exposure in our cohort of ICU patients was lower than that in healthy volunteers but not significantly different from that of other reference populations. The clinical consequence of these findings must be investigated in a pharmacokinetic-pharmacodynamic (PK-PD) study incorporating outcome in a larger cohort. (This study is registered at ClinicalTrials.gov under registration no. NCT01783379.).