Altered Micafungin Pharmacokinetics in Intensive Care Unit Patients

In Vivo Efficacy of Rezafungin, Anidulafungin, Caspofungin, and Micafungin against Four Candida auris Clades in a Neutropenic Mouse Bloodstream Infection Model

OBJECTIVES

Rezafungin is the first new drug approved to treat candidaemia and invasive candidiasis in more than 10 years. However, data are scant on the in vivo efficacy of rezafungin and the other three approved echinocandins against different Candida auris clades.

METHODS

This study involved 10 isolates representing 4 C. auris clades: South Asian (n = 2), East Asian (n = 2), South African (n = 2), and South American (n = 4, including 2 environmental isolates). In the lethality experiment and fungal tissue burden experiment (kidney, heart, and brain), cyclophosphamide-treated BALB/c male mice were intravenously infected (107 and 8 × 106 colony-forming units [CFU]/mouse, respectively). A 20 mg/kg dose of rezafungin was administered on days 1, 3, and 6. Alternatively, beginning 24 h post-infection, mice received 3 mg/kg of caspofungin, 5 mg/kg of micafungin, or 5 mg/kg of anidulafungin once daily for 6 days.

RESULTS

Regardless of isolate and clade, all echinocandin regimens improved survival after 21 days (p = 0.0041 to p < 0.0001). All echinocandins frequently produced >3-log mean CFU/g decreases in the fungal kidney and heart burdens, although some of these decreases were not statistically significant. Rezafungin, regardless of clade, produced 3-5 and 2-4 log CFU/g decreases in the kidney and heart burdens, respectively. Echinocandins did not inhibit fungal growth in the brain. Histopathological examination performed on day 7 showed no fungal cells in the heart and kidneys of rezafungin-treated mice and to a lesser extent, caspofungin-treated mice, regardless of the clinical isolate. All echinocandin-treated mice showed medium and/or large foci of fungal cells in their cerebrum or cerebellum.

CONCLUSIONS

Regardless of the C. auris clade, rezafungin activity in vivo was comparable to or improved over that of the three previously approved echinocandins.

Impact of Obesity on Echinocandin Effectiveness in Treating Candida Infections: A Retrospective Observational Cohort Study

Introduction

Echinocandins are used to treat invasive candidiasis (IC), with FDA-approved doses indicated for both obese and non-obese patients. Pharmacokinetic (PK) studies have identified subtherapeutic exposure in obese patients receiving standard doses (SDs) of echinocandins. However, research on clinical outcome differences of echinocandins' SDs between obese and non-obese patients is lacking. Therefore, this study aimed to evaluate the effectiveness of echinocandins' SDs in obese compared to normal-weight patients with IC.

Patients and Methods

This retrospective cohort study was conducted at King Saud University Medical City (KSUMC) from Jan 2017 to Feb 2023. The study included adult patients diagnosed with Candida infections who received ≥ 4 doses of echinocandins. Patients with body mass index (BMI) less than 18 kg/m2 were excluded from the study. The primary and secondary outcomes included the total length of stay (LOS), IC duration, frequency of clinical resolution and all-cause mortality.

Results

This study included 132 patients (47 obese; 85 non-obese) with a median age of 61 years. The median BMI and weight were different between the obese (34.5 kg/m2, 88 kg) and non-obese (24 kg/m2, 65 kg) groups (P= 0.01). Micafungin and caspofungin were used in 63.6% and 36.4% of patients, respectively. The total LOS and length of IC infections were similar between both groups, with median values of 29.5 days (P= 0.896) and 18 days (P = 0.160), respectively. The clinical improvement percentages were 68.1% for obese and 65.9% for non-obese patients (P= 0.797), with all-cause mortality rates at 44.7% and 42.4%, respectively (P= 0.796).

Conclusion

The study found no clinical outcome differences between obese and non-obese patients, with Similar effectiveness of the echinocandins' SDs in both groups. Further research in multi-centre settings is recommended to detect any potential differences between the two groups.

Updated antimicrobial dosing recommendations for obese patients

The prevalence of obesity has increased considerably in the last few decades. Pathophysiological changes in obese patients lead to pharmacokinetic (PK) and pharmacodynamic (PD) alterations that can condition the correct exposure to antimicrobials if standard dosages are used. Inadequate dosing in obese patients can lead to toxicity or therapeutic failure. In recent years, additional antimicrobial PK/PD data, extended infusion strategies, and studies in critically ill patients have made it possible to obtain data to provide a better dosage in obese patients. Despite this, it is usually difficult to find information on drug dosing in this population, which is sometimes contradictory. This is a comprehensive review of the dosing of different types of antimicrobials (antibiotics, antifungals, antivirals, and antituberculosis drugs) in obese patients, where the literature on PK and possible dosing strategies in obese adults was critically assessed.

Therapeutic drug monitoring of antifungal therapies: do we really need it and what are the best practices?

INTRODUCTION

Despite advancements, invasive fungal infections (IFI) still carry high mortality rates, often exceeding 30%. The challenges in diagnosis, coupled with limited effective antifungal options, make managing IFIs complex. Antifungal drugs are essential for IFI management, but their efficacy can be diminished by drug-drug interactions and pharmacokinetic variability. Therapeutic Drug Monitoring (TDM), especially in the context of triazole use, has emerged as a valuable strategy to optimize antifungal therapy.

AREAS COVERED

This review provides current evidence regarding the potential benefits of TDM in IFI management. It discusses how TDM can enhance treatment response, safety, and address altered pharmacokinetics in specific patient populations.

EXPERT OPINION

TDM plays a crucial role in achieving optimal therapeutic outcomes in IFI management, particularly for certain antifungal agents. Preclinical studies consistently show a link between therapeutic drug levels and antifungal efficacy. However, clinical research in mycology faces challenges due to patient heterogeneity and the diversity of fungal infections. TDM's potential advantages in guiding Echinocandin therapy for critically ill patients warrant further investigation. Additionally, for drugs like Posaconazole, assessing whether serum levels or alternative markers like saliva offer the best measure of efficacy is an intriguing question.

Pharmacokinetic and pharmacodynamic considerations for antifungal therapy optimisation in the treatment of intra-abdominal candidiasis

Intra-abdominal candidiasis (IAC) is one of the most common of invasive candidiasis observed in critically ill patients. It is associated with high mortality, with up to 50% of deaths attributable to delays in source control and/or the introduction of antifungal therapy. Currently, there is no comprehensive guidance on optimising antifungal dosing in the treatment of IAC among the critically ill. However, this form of abdominal sepsis presents specific pharmacokinetic (PK) alterations and pharmacodynamic (PD) challenges that risk suboptimal antifungal exposure at the site of infection in critically ill patients. This review aims to describe the peculiarities of IAC from both PK and PD perspectives, advocating an individualized approach to antifungal dosing. Additionally, all current PK/PD studies relating to IAC are reviewed in terms of strength and limitations, so that core elements for the basis of future research can be provided.

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.

Population Pharmacokinetic Model and Optimal Sampling Strategies for Micafungin in Critically Ill Patients Diagnosed with Invasive Candidiasis

Candida bloodstream infections are associated with high attributable mortality, where early initiation of adequate antifungal therapy is important to increase survival in critically ill patients. The exposure variability of micafungin, a first-line agent used for the treatment of invasive candidiasis, in critically ill patients is significant, potentially resulting in underexposure in a substantial portion of these patients. The objective of this study was to develop a population pharmacokinetic model including appropriate sampling strategies for assessing micafungin drug exposure in critically ill patients to support adequate area under the concentration-time curve (AUC) determination. A two-compartment pharmacokinetic model was developed using data from intensive care unit (ICU) patients (n = 19), with the following parameters: total body clearance (CL), volume of distribution of the central compartment (V1), inter-compartmental clearance (CL12), and volume of distribution of the peripheral compartment (V2). The final model was evaluated with bootstrap analysis and the goodness-of-fit plots for the population and individual predicted micafungin plasma concentrations. Optimal sampling strategies (with sampling every hour, 24 h per day) were developed with 1- and 2-point sampling schemes. Final model parameters (±SD) were: CL = 1.03 (0.37) (L/h/1.85 m²), V1 = 0.17 (0.07) (L/kg LBMc), CL12 = 1.80 (4.07) (L/h/1.85 m²), and V2 = 0.12 (0.06) (L/kg LBMc). Sampling strategies with acceptable accuracy and precision were developed to determine the micafungin AUC. The developed model with optimal sampling procedures provides the opportunity to achieve quick optimization of the micafungin exposure from a single blood sample using Bayesian software and may be helpful in guiding early dose decision-making.

Echinocandins - structure, mechanism of action and use in antifungal therapy

With increasing number of immunocompromised patients as well as drug resistance in fungi, the risk of fatal fungal infections in humans increases as well. The action of echinocandins is based on the inhibition of β-(1,3)-d-glucan synthesis that builds the fungal cell wall. Caspofungin, micafungin, anidulafungin and rezafungin are semi-synthetic cyclic lipopeptides. Their specific chemical structure possess a potential to obtain novel derivatives with better pharmacological properties resulting in more effective treatment, especially in infections caused by Candida and Aspergillus species. In this review we summarise information about echinocandins with closer look on their chemical structure, mechanism of action, drug resistance and usage in clinical practice. We also introduce actual trends in modification of this antifungals as well as new methods of their administration, and additional use in viral and bacterial infections.

Therapeutic Drug Monitoring of the Echinocandin Antifungal Agents: Is There a Role in Clinical Practice? A Position Statement of the Anti-Infective Drugs Committee of the International Association of Therapeutic Drug Monitoring and Clinical Toxicology

PURPOSE

Reduced exposure to echinocandins has been reported in specific patient populations, such as critically ill patients; however, fixed dosing strategies are still used. The present review examines the accumulated evidence supporting echinocandin therapeutic drug monitoring (TDM) and summarizes available assays and sampling strategies.

METHODS

A literature search was conducted using PubMed in December 2020, with search terms such as echinocandins, anidulafungin, caspofungin, micafungin, or rezafungin with pharmacology, pharmacokinetics (PKs), pharmacodynamics (PDs), drug-drug interactions, TDM, resistance, drug susceptibility testing, toxicity, adverse drug reactions, bioanalysis, chromatography, and mass spectrometry. Data on PD/PD (PK/PD) outcome markers, drug resistance, PK variability, drug-drug interactions, assays, and TDM sampling strategies were summarized.

RESULTS

Echinocandins demonstrate drug exposure-efficacy relationships, and maximum concentration/minimal inhibitory concentration ratio (Cmax/MIC) and area under the concentration-time curve/MIC ratio (AUC/MIC) are proposed PK/PD markers for clinical response. The relationship between drug exposure and toxicity remains poorly clarified. TDM could be valuable in patients at risk of low drug exposure, such as those with critical illness and/or obesity. TDM of echinocandins may also be useful in patients with moderate liver impairment, drug-drug interactions, hypoalbuminemia, and those undergoing extracorporeal membrane oxygenation, as these conditions are associated with altered exposure to caspofungin and/or micafungin. Assays are available to measure anidulafungin, micafungin, and caspofungin concentrations. A limited-sampling strategy for anidulafungin has been reported.

CONCLUSIONS

Echinocandin TDM should be considered in patients at known risk of suboptimal drug exposure. However, for implementing TDM, clinical validation of PK/PD targets is needed.

A Loading Micafungin Dose in Critically Ill Patients Undergoing Continuous Venovenous Hemofiltration or Continuous Venovenous Hemodiafiltration: A Population Pharmacokinetic Analysis

BACKGROUND

In this study, the authors aimed to compare the pharmacokinetics (PK) of micafungin in critically ill patients receiving continuous venovenous hemofiltration (CVVH, 30 mL·kg-1·h-1) with those of patients receiving equidoses of hemodiafiltration (CVVHDF, 15 mL·kg-1·h-1 + 15 mL·kg-1·h-1) and determine the optimal dosing regimen using the developed model.

METHODS

Patients with septic shock undergoing continuous renal replacement therapy and receiving a conventional dose of 100 mg micafungin once daily were eligible for inclusion. Total micafungin plasma concentrations from 8 CVVH sessions and 8 CVVHDF sessions were subjected to a population PK analysis using Pmetrics. Validation of the model performance was reinforced by external validation. Monte Carlo simulations were performed considering the total ratio of free drug area under the curve (AUC) over 24 hours to the minimum inhibitory concentration (MIC) (AUC0-24/MIC) in plasma.

RESULTS

The median total body weight (min-max) was 94.8 (66-138) kg. Micafungin concentrations were best described by a 2-compartmental PK model. No covariates, including continuous renal replacement therapy modality (CVVH or CVVHDF), were retained in the final model. The mean parameter estimates (SD) were 0.96 (0.32) L/h for clearance and 14.8 (5.3) L for the central compartment volume. External validation confirmed the performance of the developed PK model. Dosing simulations did not support the use of standard 100 mg daily dosing, except for Candida albicans on the second day of therapy. A loading dose of 150 mg followed by 100 mg daily reached the probability of target attainment for all C. albicans and C. glabrata, but not for C. krusei and C. parapsilosis.

CONCLUSIONS

No difference was observed in micafungin PK between equidoses of CVVH and CVVHDF. A loading dose of 150 mg is required to achieve the PK/PD target for less susceptible Candida species from the first day of therapy.

Penetration of echinocandins into wound secretion of critically ill patients

Purpose

Wound infections caused by Candida are life-threatening and difficult to treat. Echinocandins are highly effective against Candida species and recommended for treatment of invasive candidiasis. As penetration of echinocandins into wounds is largely unknown, we measured the concentrations of the echinocandins anidulafungin (AFG), micafungin (MFG), and caspofungin (CAS) in wound secretion (WS) and in plasma of critically ill patients.

Methods

We included critically ill adults with an indwelling wound drainage or undergoing vacuum-assisted closure therapy, who were treated with an echinocandin for suspected or proven invasive fungal infection. Concentrations were measured by liquid chromatography with UV (AFG and MFG) or tandem mass spectrometry detection (CAS).

Results

Twenty-one patients were enrolled. From eight patients, serial WS samples and simultaneous plasma samples were obtained within a dosage interval. AFG concentrations in WS amounted to < 0.025–2.25 mg/L, MFG concentrations were 0.025–2.53 mg/L, and CAS achieved concentrations of 0.18–4.04 mg/L. Concentrations in WS were significantly lower than the simultaneous plasma concentrations and below the MIC values of some relevant pathogens.

Conclusion

Echinocandin penetration into WS displays a high inter-individual variability. In WS of some of the patients, concentrations may be sub-therapeutic. However, the relevance of sub-therapeutic concentrations is unknown as no correlation has been established between concentration data and clinical outcome. Nevertheless, in the absence of clinical outcome studies, our data do not support the use of echinocandins at standard doses for the treatment of fungal wound infections, but underline the pivotal role of surgical debridement.

Supplementary Information

The online version contains supplementary material available at 10.1007/s15010-021-01604-x.

Pharmacokinetic Drug-drug Interaction of Antibiotics Used in Sepsis Care in China

BACKGROUND

Many antibiotics have a high potential for interactions with drugs, as a perpetrator and/or victim, in critically ill patients, and particularly in sepsis patients.

METHODS

The aim of this review is to summarize the pharmacokinetic drug-drug interaction (DDI) of 45 antibiotics commonly used in sepsis care in China. Literature search was conducted to obtain human pharmacokinetics/ dispositions of the antibiotics, their interactions with drug-metabolizing enzymes or transporters, and their associated clinical drug interactions. Potential DDI is indicated by a DDI index ≥ 0.1 for inhibition or a treatedcell/ untreated-cell ratio of enzyme activity being ≥ 2 for induction.

RESULTS

The literature-mined information on human pharmacokinetics of the identified antibiotics and their potential drug interactions is summarized.

CONCLUSION

Antibiotic-perpetrated drug interactions, involving P450 enzyme inhibition, have been reported for four lipophilic antibacterials (ciprofloxacin, erythromycin, trimethoprim, and trimethoprim-sulfamethoxazole) and three antifungals (fluconazole, itraconazole, and voriconazole). In addition, seven hydrophilic antibacterials (ceftriaxone, cefamandole, piperacillin, penicillin G, amikacin, metronidazole, and linezolid) inhibit drug transporters in vitro. Despite no clinical PK drug interactions with the transporters, caution is advised in the use of these antibacterials. Eight hydrophilic antibiotics (all β-lactams; meropenem, cefotaxime, cefazolin, piperacillin, ticarcillin, penicillin G, ampicillin, and flucloxacillin), are potential victims of drug interactions due to transporter inhibition. Rifampin is reported to perpetrate drug interactions by inducing CYP3A or inhibiting OATP1B; it is also reported to be a victim of drug interactions, due to the dual inhibition of CYP3A4 and OATP1B by indinavir. In addition, three antifungals (caspofungin, itraconazole, and voriconazole) are reported to be victims of drug interactions because of P450 enzyme induction. Reports for other antibiotics acting as victims in drug interactions are scarce.

Optimization of Micafungin Dosage for Chinese Patients with Sepsis in the Intensive Care Unit Based on a Population Pharmacokinetic-Pharmacodynamic Analysis

PURPOSE

This study aimed to identify parameters that influence micafungin pharmacokinetics in Chinese patients with sepsis in the intensive care unit and optimize micafungin dosage by determining the probability of reaching pharmacodynamic targets.

METHODS

Blood samples were collected from 32 Chinese patients with sepsis who were treated with micafungin. The samples were analyzed and used to build a population pharmacokinetic model. Monte Carlo simulations were performed to estimate the probability of achieving adequate plasma levels of micafungin against Candida species.

RESULTS

Alanine aminotransferase and sequential organ failure assessment score were found to significantly influence the clearance and peripheral distribution volume of micafungin, respectively. Monte Carlo simulations based on area under the plasma concentration-time curve over 24 h showed that patients must be administered at least 200 and 250 mg micafungin daily to reach minimum inhibitory concentration breakpoints of 0.032 and 0.064 mg/L for Candida glabrata and Candida tropicalis, respectively. Additionally, a probability of target attainment of ≥ 90% could not be achieved for Candida krusei or Candida parapsilosis with a 300 mg daily dose.

CONCLUSIONS

The recommended daily dose of micafungin (100 mg) may produce low clinical success ratios in non-Candida albicans infections; therefore, higher doses should be administered to improve clinical outcomes.

Pharmacokinetic/pharmacodynamics variability of echinocandins in critically ill patients: A systematic review and meta-analysis

WHAT IS KNOWN AND OBJECTIVE

Anidulafungin, caspofungin and micafungin are three widely used echinocandin drugs licensed for the treatment of invasive fungal infections, and their clinical use is widespread. To evaluate pharmacokinetic/pharmacodynamics variability of echinocandins in critically ill patients by comparing the differences in pharmacokinetic parameters between critically ill patients and healthy volunteers or general patients.

METHODS

MEDLINE, EMBASE, The Cochrane Library and Pubmed were searched from inception until 6 September 2018. Studies investigating the pharmacokinetic parameters of echinocandins in critically ill patients, healthy volunteers or general patients were included. Our primary outcomes included AUC0-24 h , Cmax and Cmin (24 hours). Two reviewers independently reviewed all titles, abstracts and text, and extracted data. We applied R software (R 2017) to conduct meta-analysis.

RESULTS AND DISCUSSION

Of 3235 articles screened, 17 studies were included in the data synthesis. Descriptive data from single-arm studies show that critically ill patients who received caspofungin had more stable AUC0-24 h than those who received anidulafungin and micafungin. The Cmax of critically ill patients who received caspofungin and micafungin was similar to healthy volunteers. However, the Cmax in critically ill patients who received anidulafungin was lower than in healthy volunteers. The Cmin and T1/2 of critically ill patients who received caspofungin were larger than in healthy volunteers. The Vd and CL of critically ill patients receiving anidulafungin and micafungin were larger than in healthy volunteers.

WHAT IS NEW AND CONCLUSION

This systematic review provides an analysis of the pharmacokinetic/pharmacodynamics variability of echinocandins in critically ill patients. Based on the limited data available, caspofungin has less pharmacokinetic/pharmacodynamics variability than anidulafungin and micafungin.

Population pharmacokinetics of micafungin over repeated doses in critically ill patients: a need for a loading dose?

OBJECTIVES

To study the population pharmacokinetics of micafungin in critically ill patients, evaluate and optimize dosage regimens.

METHODS

An HPLC-fluorescence bioassay for micafungin was developed, fully validated and applied to a pharmacokinetic study conducted in 14 ICU patients. Dense blood sampling was performed from days 1 to 7. A population pharmacokinetic model accounting for interindividual (IIV) and interoccasion variability (IOV) of the PK parameters was developed. Simulations were performed to estimate the probability of target attainment (PTA) for several dosing regimens.

KEY FINDINGS

A two-compartment pharmacokinetic model best described the data, with population clearance CL = 1.31 L/h and central volume V1 = 14.2 L. The relatively high IOV observed (45% for CL, 27% for V1) sets limits for the dose individualization in this population. The low PTA on the first day of treatment suggests the need of a loading dose. PTA and CFR estimates show that the current micafungin dosage may be insufficient for the treatment of borderline susceptible Candida strains.

CONCLUSIONS

A loading dose of up to 300 mg of micafungin is needed for the treatment of invasive candidiasis in ICU patients while a maintenance dose of up to 200 mg can be considered in empirical antifungal treatment.

Comparative pharmacokinetics of the three echinocandins in ICU patients

Background

We conducted a prospective study in ICU patients of two tertiary hospitals in order to determine basic pharmacokinetic (PK) parameters, associated variation and target attainment rates for anidulafungin, micafungin and caspofungin.

Methods

Serum samples from patients treated for 7 days with the standard doses of anidulafungin (N = 13), micafungin (N = 14) or caspofungin (N = 7) were analysed by validated chromatographic methods. PK parameters determined with non-compartmental analysis were correlated with demographic, laboratory and disease severity characteristics. The percentages of patients attaining drug exposures described in the summary of product characteristics (SmPC) documents and preclinical PK/PD targets for stasis were estimated.

Results

The median (range) AUC24 was 101.46 (54.95–274.15) mg·h/L for anidulafungin, 79.35 (28.00–149.30) mg·h/L for micafungin and 48.46 (19.44–103.69) mg·h/L for caspofungin. The interindividual variability of anidulafungin, micafungin and caspofungin AUC24 was 46%–58%, attributed mainly to variability in volume of distribution (V), clearance (CL) and in both V and CL, respectively. Significant correlations were found between anidulafungin AUC24 and BMI (rs = −0.670, P = 0.012) and liver enzymes (rs = 0.572–0.665, P = 0.013–0.041) and between caspofungin Cmin and transaminase levels (rs = −0.775 to −0.786, P = 0.036–0.041). Less than 50% of our patients attained the corresponding SmPC median AUC24s and none of the patients attained the PK/PD targets for Candida albicans and Candida parapsilosis.

Conclusions

Anidulafungin exposure in ICU patients was comparable with that reported in non-ICU patients and in healthy volunteers. Micafungin exposure was comparable to that of other patients but ∼30% lower than that in healthy volunteers, whereas caspofungin exposure was rather low (∼50% lower than in healthy volunteers). Larger interindividual variability (50%–60%) was recorded in ICU patients compared with other groups for all three echinocandins.

Persistent candida arthritis successfully treated with micafungin instillation and surgery. A case report

We report a rare case of C. krusei knee arthritis treated with instillation of micafungin and arthroscopy. A 49-year-old man hospitalized for treatment of Acute Myeloid Leukemia developed knee arthritis with C. krusei. He was treated with a combination of arthroscopic debridement, intravenous as well as intra-articular micafungin. Serum and intra-articular concentrations of micafungin were determined. After instillation of micafungin in the knee and arthroscopic debridement, the patient completely recovered.

Pharmacokinetics of Micafungin in Critically Ill Patients

We investigated covariates of pharmacokinetics of micafungin in critically ill patients. After application of micafungin, plasma samples were collected. Non-linear mixed effects modelling (NONMEM 7.3) was used to develop the pharmacokinetic model. Using this model, the adequacy of a fixed 100 mg dosing regimen was evaluated in the study cohort. A two-compartment model with linear elimination was found to describe the obtained data. SOFA score was identified as a significant covariate on both clearance and central volume of distribution, respectively. Patients in highly critical condition, represented by a SOFA above 10 showed a 30.8% lower central volume of distribution than the less critically ill patients. For patients with bilirubin levels above 4 mg/dl, clearance was decreased by 21.1%. Renal replacement therapy (RRT) did not influence micafungin clearance or the volumes of distribution. In a posthoc evaluation of the modeled population, 100 mg micafungin was suitable when assessing the PKPD targets (AUC/MIC) for C. albicans and C. glabrata, with insufficient target attainment for C. parapsilosis. Micafungin pharmacokinetics appear not to be influenced by the status of RRT. A dose of 100 mg micafungin is suitable for infections with C. albicans and C. glabrata in critically ill patients.

Impact of Initial Antifungal Therapy on the Outcome of Patients With Candidemia and Septic Shock Admitted to Medical Wards: A Propensity Score-Adjusted Analysis

Background

Echinocandins are recommended as firstline therapy in patients with candidemia. However, there is debate on their efficacy in survival outcomes. The aim of this study is to evaluate whether the choice of initial antifungal therapy improves mortality in patients with candidemia in relation to the presence of septic shock.

Methods

Patients with candidemia hospitalized in internal medicine wards of 5 tertiary care centers were included in the study (December 2012–December 2014). Patient characteristics, therapeutic interventions, and outcome were reviewed. Propensity score (PS) was used as a covariate of the multivariate analysis to perform a stratified analysis according to PS quartiles and to match patients receiving “echinocandins” or “azoles.”

Results

Overall, 439 patients with candidemia were included in the study. A total of 172 (39.2%) patients had septic shock. Thirty-day mortality was significantly higher in patients with septic shock (45.3%) compared with those without septic shock (31.5%; P = .003). Among patients with septic shock, the use of echinocandins in the first 48 hours, compared with azoles, did not affect 30-day mortality in the PS-adjusted Cox regression analysis (hazard ratio [HR], 0.77; 95% confidence interval [CI], 0.37–1.59; P = .48), the PS-stratified analysis, or the logistic regression model in matched cohorts (adjusted HR, 0.92; 95% CI, 0.51–1.63; P = .77).

Conclusions

Echinocandin therapy seems not to improve the outcome of non–intensive care unit patients with septic shock due to candidemia. These findings support the urgent need of further studies in this patient population.

Fluconazole is not inferior than caspofungin, micafungin or amphotericin B in the presence of 50% human serum against Candida albicans and Candida parapsilosis biofilms

Biofilm formation is a relevant risk factor for mortality in candidemia. Data about serum-based susceptibility testing against Candida biofilms are scant; therefore, the activity of fluconazole, amphotericin B, caspofungin and micafungin was determined against Candida albicans and C. parapsilosis biofilms with or without 50% human serum using XTT-based assays. Serum caused a remarkable adverse effect regarding biofilm structure for both species. Additionally, the ratio of nonviable cells increased for C. parapsilosis biofilms, as confirmed by fluorescent microscopy and flow cytometry. Despite impaired biofilm development, traditionally biofilm-active antifungals, surprisingly, showed decreased activity against C. albicans biofilms in serum at concentrations ranging from 0.5 to 1 mg/l and from 0.015 to 1 mg/l for amphotericin B and echinocandins, respectively (P < .01-.05). However, C. parapsilosis showed higher susceptibility to these antifungals due to reduced biofilm mass and the fungicidal effect of serum at concentrations ranging from 0.015 to 1 mg/l and from 0.015 to 512 mg/l for amphotericin B and echinocandins, respectively (P < .01-.05). Fluconazole exerted better antifungal activity in serum than traditionally biofilm-active antifungals against both examined biofilms. For fluconazole, significant differences were observed in susceptibility between serum-treated and serum-free biofilms at concentrations ranging from 0.015 to 8 mg/l and from 0.03 to 512 mg/l for C. albicans and C. parapsilosis isolates, respectively (P < .01-.05). The high antifungal activity of fluconazole in 50% serum both against C. albicans and C. parapsilosis biofilms supports the utility of fluconazole prophylaxis to reduce the risk of catheter-associated fungal infections.

Clinical Pharmacokinetics and Pharmacodynamics of Micafungin

Micafungin is a selective inhibitor of the synthesis of fungal 1,3-β-d-glucan, an essential component of the fungal cell wall. It is available as a powder for infusion only and is registered for the treatment of invasive and esophageal candidiasis in addition to prophylaxis of Candida infections in both adults and children. Average exposure after a single intravenous 100 mg dose in healthy adults is 133 mg h/L. Both exposure and maximum plasma concentration show linear dose proportional pharmacokinetics (PK) over a 0.15–8 mg/kg dose range. In healthy adults, the clearance (CL) is 10.4 mL/h/kg and volume of distribution is 0.2 L/kg; both are independent of the dose. Micafungin is metabolized by arylsulfatase, catechol-O-methyltransferase, and several cytochrome P450 (CYP) isoenzymes (3A4, 1A2, 2B6 and 2C), but no dose adjustments are necessary in patients with (severe) hepatic dysfunction. Exposure to micafungin is lower in hematology patients, and is even further lowered in critically ill patients (including burn patients) compared with healthy volunteers, which might have consequences for treatment efficacy. In children, an increased CL has been reported: 40–80 mL/h/kg in premature neonates and 20 mL/h/kg in children >4 months of age. Therefore, relatively higher doses of 4–10 mg/kg in premature neonates and 2–4 mg/kg in children with invasive candidiasis are used. However, these higher CLs may also be explained by the eightfold higher free fraction of unbound micafungin in premature neonates, meaning that an augmented dose might not be required.

In vitro antifungal susceptibility patterns of planktonic and sessile Candida kefyr clinical isolates

The activity of fluconazole, amphotericin B, caspofungin and micafungin was determined using XTT-based fungal damage assays against planktonic cells, early and mature biofilms of Candida kefyr. Median MICs of planktonic cells were 0.25 mg/l, 0.25 mg/l, 0.5 mg/l, and 0.06 mg/l for fluconazole, amphotericin B, caspofungin, and micafungin, respectively. Fluconazole showed at least 50% fungal damage at ≥4 mg/l (51.5% ± 6.63% to 78.38% ± 1.44%) and at ≥128 mg/l (57.88% ± 9.2% to 67.25% ± 9.59%), while amphotericin B produced an even higher anti-biofilm effect at ≥0.5 mg/l (64.63% ± 6.79% to 79.5% ± 5.9%) and at ≥0.12 mg/l (77.63% ± 8.43% to 92.75% ± 1.89%) against early and mature biofilms, respectively. In case of micafungin, 50% fungal damage was observed at ≥0.06 mg/l (66.88% ± 10.16% to 98.63% ± 1.24%) and ≥0.25 mg/l (74.13% ± 10.77% to 99.38% ± 0.38%) for early and mature biofilms, respectively. Caspofungin-exposed cells showed an unexpected susceptibility pattern, that is, planktonic cells showed significantly decreased susceptibility at concentrations ranging from 0.015 mg/l to 1 mg/l compared to biofilms (P < .05-.01). The damage in planktonic cells and biofilms was comparable at higher concentrations. For planktonic cells and biofilms, 50% fungal damage was observed first at 0.5 mg/l (59.75% ± 3.16%) and at 0.06 mg/l (70.25% ± 10.95%), respectively. This unexpected pattern was confirmed using scanning electron microscopy. The unusual susceptibility pattern observed at lower caspofungin concentrations may explain the poorer outcome of caspofungin-treated C. kefyr infections documented in certain patient populations. As this phenomenon was markedly less apparent in case of micafungin, these data suggest that micafungin may be a more reliable option than caspofungin for the treatment of C. kefyr infections.

ESICM/ESCMID task force on practical management of invasive candidiasis in critically ill patients

INTRODUCTION

The term invasive candidiasis (IC) refers to both bloodstream and deep-seated invasive infections, such as peritonitis, caused by Candida species. Several guidelines on the management of candidemia and invasive infection due to Candida species have recently been published, but none of them focuses specifically on critically ill patients admitted to intensive care units (ICUs).

MATERIAL AND METHODS

In the absence of available scientific evidence, the resulting recommendations are based solely on epidemiological and clinical evidence in conjunction with expert opinion. The task force used the GRADE (Grading of Recommendations Assessment, Development, and Evaluation) approach to evaluate the recommendations and assign levels of evidence. The recommendations and their strength were decided by consensus and, if necessary, by vote (modified Delphi process). Descriptive statistics were used to analyze the results of the Delphi process. Statements obtaining > 80% agreement were considered to have achieved consensus.

CONCLUSIONS

The heterogeneity of this patient population necessitated the creation of a mixed working group comprising experts in clinical microbiology, infectious diseases and intensive care medicine, all chosen on the basis of their expertise in the management of IC and/or research methodology. The working group's main goal was to provide clinicians with clear and practical recommendations to optimize microbiological diagnosis and treatment of IC. The Systemic Inflammation and Sepsis and Infection sections of the European Society of Intensive Care Medicine (ESICM) and the Critically Ill Patients Study Group of the European Society of Clinical Microbiology and Infectious Diseases (ESCMID) therefore decided to develop a set of recommendations for application in non-immunocompromised critically ill patients.

Overview of antifungal dosing in invasive candidiasis

In the past, most antifungal therapy dosing recommendations for invasive candidiasis followed a 'one-size fits all' approach with recommendations for lowering maintenance dosages for some antifungals in the setting of renal or hepatic impairment. A growing body of pharmacokinetic/pharmacodynamic research, however now points to a widespread 'silent epidemic' of antifungal underdosing for invasive candidiasis, especially among critically ill patients or special populations who have altered volume of distribution, protein binding and drug clearance. In this review, we explore how current adult dosing recommendations for antifungal therapy in invasive candidiasis have evolved, and special populations where new approaches to dose optimization or therapeutic drug monitoring may be needed, especially in light of increasing antifungal resistance among Candida spp.

Poor in vivo efficacy of caspofungin, micafungin and amphotericin B against wild-type Candida krusei clinical isolates does not correlate with in vitro susceptibility results

We determined micafungin, caspofungin and amphotericin B (AMB) minimum inhibitory concentration (MICs) and killing rates in RPMI-1640 and in RPMI-1640 with 50% serum against three Candida krusei bloodstream isolates. MIC ranges in RPMI-1640 were 0.125-0.25, 0.25 and 0.125-0.5 mg/L, in RPMI-1640 with 50% serum, MICs were 64-128-, 8- and 4-16-fold higher, respectively. In RPMI-1640 micafungin and caspofungin at 1, 4, 16 and 32 mg/L as well as AMB at 2 mg/L were fungicidal against all isolates in ≤3.96, ≤4.42 and 14.96 h, respectively. In RPMI-1640 with 50% serum, caspofungin was fungicidal for all isolates only at 32 mg/L, micafungin and AMB were fungistatic. In neutropenic mice, 5 mg/kg caspofungin and 1 mg/kg AMB were ineffective against two of the three isolates. Thus, in vivo efficacy of echinocandins and AMB is weak or absent against C. krusei. Prescribers treating C. krusei infections with echinocandins should watch out for clinical resistance and therapeutic failure.

Simple and robust LC–MS/MS analysis method for therapeutic drug monitoring of micafungin

Aim: To develop a simple and robust LC–MS/MS method to quantify concentrations of micafungin in human plasma for pharmacokinetic studies and therapeutic drug monitoring. Methods: Sample preparation involved protein precipitation with acetonitrile:methanol (83:17% v/v) and [13C6]-micafungin as internal standard. A rapid and selective method for micafungin was validated across a range of 0.200–10.0 mg/l. Results: The calculated accuracy for the eight-point calibration ranged from 0.7 to 5.3%. Within-run precision ranged from 0.8 to 5.9%, between-run precision ranged from 0.7 to 3.1%, and overall precision ranged from 1.3 to 6.6%. Conclusion: A simple and robust LC–MS/MS method for analyzing micafungin in human plasma has been validated and was utilized for quantification of micafungin.

Echinocandins for management of invasive candidiasis in patients with liver disease and liver transplantation

Candida species remains one of the most important causes of opportunistic infections worldwide. Invasive candidiasis (IC) is associated with considerable morbidity and mortality in liver disease (LD) patients if not treated promptly. Echinocandins are often recommended as a first-line empirical treatment for managing IC and can especially play a critical role in managing IC in LD patients. However, advanced LD patients are often immunocompromised and critically ill. Hence altered pharmacokinetics, drug interactions as well as tolerance issues of antifungal treatments are a concern in these patients. This comprehensive review examines the epidemiology, risk factors and diagnosis of IC in patients with LD and evaluates differences between three available echinocandins for treating this group of patients.

Population pharmacokinetics/pharmacodynamics of micafungin against Candida species in obese, critically ill, and morbidly obese critically ill patients

Background

Dosing in obese critically ill patients is challenging due to pathophysiological changes derived from obesity and/or critical illness, and it remains fully unexplored. This study estimated the micafungin probability of reaching adequate 24-h area under the curve (AUC_0–24h)/minimum inhibitory concentration (MIC) values against Candida spp. for an obese/nonobese, critically ill/noncritically ill, large population.

Methods

Blood samples for pharmacokinetic analyses were collected from 10 critically ill nonobese patients, 10 noncritically ill obese patients, and 11 critically ill morbidly obese patients under empirical/directed micafungin treatment. Patients received once daily 100–150 mg micafungin at the discretion of the treating physician following the prescribing information and hospital guidelines. Total micafungin concentrations were determined by high-performance liquid chromatography (HPLC). Monte-Carlo simulations were performed and the probability of target attainment (PTA) was calculated using the AUC_0–24/MIC cut-offs 285 (C. parapsilosis), 3000 (all Candida spp.), and 5000 (nonparapsilosis Candida spp.). Intravenous once-daily 100-mg, 150-mg, and 200-mg doses were simulated at different body weights (45, 80, 115, 150, and 185 kg) and age (30, 50, 70 and 90 years old). PTAs ≥ 90% were considered optimal. Fractional target attainment (FTA) was calculated using published MIC distributions. A dosing regimen was considered successful if the FTA was ≥ 90%.

Results

Overall, 100 mg of micafungin was once-daily administered for nonobese and obese patients with body mass index (BMI) ≤ 45 kg/m² and 150 mg for morbidly obese patients with BMI > 45 kg/m² (except two noncritically ill obese patients with BMI ~ 35 kg/m² receiving 150 mg, and one critically ill patient with BMI > 45 kg/m² receiving 100 mg). Micafungin concentrations in plasma were best described using a two-compartment model. Weight and age (but not severity score) were significant covariates and improved the model. FTAs > 90% were obtained against C. albicans with the 200 mg/24 h dose for all body weights (up to 185 kg), and with the 150 mg/24 h for body weights < 115 kg, and against C. glabrata with the 200 mg/24 h dose for body weights < 115 kg.

Conclusion

The lack of adequacy for the 100 mg/24 h dose suggested the need to increase the dose to 150 mg/24 h for C. albicans infections. Further pharmacokinetic/pharmacodynamic studies should address optimization of micafungin dosing for nonalbicans Candida infections.

Pharmacokinetic Properties of Micafungin in Critically Ill Patients Diagnosed with Invasive Candidiasis

The estimated attributable mortality rate for invasive candidiasis (IC) in the intensive care unit (ICU) setting varies from 30 to 40%. Physiological changes in critically ill patients may affect the distribution and elimination of micafungin, and therefore, dosing adjustments might be mandatory. The objective of this study was to determine the pharmacokinetic parameters of micafungin in critically ill patients and assess the probability of target attainment. Micafungin plasma concentrations were measured to estimate the pharmacokinetic properties of micafungin. MIC values for Candida isolates were determined to assess the probability of target attainment for patients. Data from 19 patients with suspected or proven invasive candidiasis were available for analysis. The median area under the concentration-time curve from 0 to 24 h at steady state (AUC_0-24) was 89.6 mg · h/liter (interquartile range [IQR], 75.4 to 113.6 mg · h/liter); this was significantly lower than the median micafungin AUC_0-24 values of 152.0 mg · h/liter (IQR, 136.0 to 162.0 mg · h/liter) and 134.0 mg · h/liter (IQR, 118.0 to 148.6 mg · h/liter) in healthy volunteers (P = <0.0001 and P = <0.001, respectively). All Candida isolates were susceptible to micafungin, with a median MIC of 0.016 mg/liter (IQR, 0.012 to 0.023 mg/liter). The median AUC_0-24/MIC ratio was 5,684 (IQR, 4,325 to 7,578), and 3 of the 17 evaluable patients (17.6%) diagnosed with proven invasive candidiasis did not meet the AUC/MIC ratio target of 5,000. Micafungin exposure was lower in critically ill patients than in healthy volunteers. The variability in micafungin exposure in this ICU population could be explained by the patients' body weight. Our findings suggest that healthier patients (sequential organ failure assessment [SOFA] score of <10) weighing more than 100 kg and receiving 100 mg micafungin daily are at risk for inappropriate micafungin exposure and potentially inadequate antifungal treatment. (This study has been registered at ClinicalTrials.gov under identifier NCT01716988.).

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.

Pharmacokinetics of antifungal drugs: practical implications for optimized treatment of patients

Introduction

Because of the high mortality of invasive fungal infections (IFIs), appropriate exposure to antifungals appears to be crucial for therapeutic efficacy and safety.

Materials and methods

This review summarises published pharmacokinetic data on systemically administered antifungals focusing on co-morbidities, target-site penetration, and combination antifungal therapy.

Conclusions and discussion

Amphotericin B is eliminated unchanged via urine and faeces. Flucytosine and fluconazole display low protein binding and are eliminated by the kidney. Itraconazole, voriconazole, posaconazole and isavuconazole are metabolised in the liver. Azoles are substrates and inhibitors of cytochrome P450 (CYP) isoenzymes and are therefore involved in numerous drug–drug interactions. Anidulafungin is spontaneously degraded in the plasma. Caspofungin and micafungin undergo enzymatic metabolism in the liver, which is independent of CYP. Although several drug–drug interactions occur during caspofungin and micafungin treatment, echinocandins display a lower potential for drug–drug interactions. Flucytosine and azoles penetrate into most of relevant tissues. Amphotericin B accumulates in the liver and in the spleen. Its concentrations in lung and kidney are intermediate and relatively low myocardium and brain. Tissue distribution of echinocandins is similar to that of amphotericin. Combination antifungal therapy is established for cryptococcosis but controversial in other IFIs such as invasive aspergillosis and mucormycosis.

Killing Activity of Micafungin Against Candida albicans, C. dubliniensis and Candida africana in the Presence of Human Serum

We compared killing activity of micafungin in time-kill experiments in RPMI-1640 with and without 50% serum against Candida albicans, Candida dubliniensis and Candida africana reference strains and clinical isolates. Killing rates (k values) were determined for each strain and concentration. In RPMI-1640 MIC ranges were 0.015-0.03, 0.015-0.03 and 0.015 mg/L against C. albicans, C. dubliniensis and C. africana, respectively. In 50% serum MIC values for the three species increased 16- to 64-fold. In RPMI-1640 micafungin was fungicidal against two of three C. albicans isolates at 16 and 32 mg/L within 14.54 h and fungistatic against all C. africana and C. dubliniensis. Fifty per cent serum significantly decreased the growth rate of C. africana, but not of the other two species; weak in vivo replication ability of C. africana was confirmed in murine model. In 50% serum micafungin at 0.25 and 1 mg/L did not inhibit any of the three species (k values were always negative). Micafungin killing rate in 50% serum at 4, 16 and 32 mg/L was significantly decreased for C. albicans, but increased for C. dubliniensis compared to RPMI-1640. Killing activity of micafungin against C. africana was comparable or higher in 50% serum than in RPMI-1640. Although micafungin is a highly protein-bound drug, it was equally effective against the species of the C. albicans complex in 50% serum at therapeutic trough concentration (4 mg/L). Both in vitro and in vivo data confirmed the low virulence of C. africana compared to the two sibling species.

Pharmacokinetics of Anidulafungin in Critically Ill Intensive Care Unit Patients with Suspected or Proven Invasive Fungal Infections

Echinocandins, such as anidulafungin, are the first-line treatment for candidemia or invasive candidiasis in critically ill patients. There are conflicting data on the pharmacokinetic properties of anidulafungin in intensive care unit (ICU) patients. Adult ICU patients (from 3 hospitals) receiving anidulafungin for suspected or proven fungal infections were included in the present study. Patients were considered evaluable if a pharmacokinetic curve for day 3 could be completed. Twenty-three of 36 patients (7 female and 16 male) were evaluable. The median (range) age and body weight were 66 (28 to 88) years and 76 (50 to 115) kg, respectively. Pharmacokinetic sampling on day 3 (n = 23) resulted in a median anidulafungin area under the concentration-time curve from 0 to 24 h (AUC_0-24) of 72.1 (interquartile range [IQR], 61.3 to 94.0) mg · h · liter^-1, a median daily trough concentration (C₂₄) of 2.2 (IQR, 1.9 to 2.9) mg/liter, a median maximum concentration of drug in serum (C_max) of 5.3 (IQR, 4.1 to 6.0) mg/liter, a median volume of distribution (V) of 46.0 (IQR, 32.2 to 60.2) liters, and a median clearance (CL) of 1.4 (IQR, 1.1 to 1.6) liters · h^-1 Pharmacokinetic sampling on day 7 (n = 13) resulted in a median AUC_0-24 of 82.7 (IQR, 73.0 to 129.5) mg · h · liter^-1, a median minimum concentration of drug in serum (C_min) of 2.8 (IQR, 2.2 to 4.2) mg/liter, a median C_max of 5.9 (IQR, 4.6 to 8.0) mg/liter, a median V of 39.7 (IQR, 32.2 to 54.4) liters, and a median CL of 1.2 (IQR, 0.8 to 1.4) liters · h^-1 The geometric mean ratio for the AUC_day7/AUC_day3 term was 1.13 (90% confidence interval [CI], 1.03 to 1.25). The exposure in the ICU patient population was in accordance with previous reports on anidulafungin pharmacokinetics in ICU patients but was lower than that for healthy volunteers or other patient populations. Larger cohorts of patients or pooled data analyses are necessary to retrieve relevant covariates. (This study has been registered at ClinicalTrials.gov under identifier NCT01438216.).

Comparative Population Plasma and Tissue Pharmacokinetics of Micafungin in Critically Ill Patients with Severe Burn Injuries and Patients with Complicated Intra-Abdominal Infection

Severely burned patients have altered drug pharmacokinetics (PKs), but it is unclear how different they are from those in other critically ill patient groups. The aim of the present study was to compare the population pharmacokinetics of micafungin in the plasma and burn eschar of severely burned patients with those of micafungin in the plasma and peritoneal fluid of postsurgical critically ill patients with intra-abdominal infection. Fifteen burn patients were compared with 10 patients with intra-abdominal infection; all patients were treated with 100 to 150 mg/day of micafungin. Micafungin concentrations in serial blood, peritoneal fluid, and burn tissue samples were determined and were subjected to a population pharmacokinetic analysis. The probability of target attainment was calculated using area under the concentration-time curve from 0 to 24 h/MIC cutoffs of 285 for Candida parapsilosis and 3,000 for non-parapsilosis Candida spp. by Monte Carlo simulations. Twenty-five patients (18 males; median age, 50 years; age range, 38 to 67 years; median total body surface area burned, 50%; range of total body surface area burned, 35 to 65%) were included. A three-compartment model described the data, and only the rate constant for the drug distribution from the tissue fluid to the central compartment was statistically significantly different between the burn and intra-abdominal infection patients (0.47 ± 0.47 versus 0.15 ± 0.06 h(-1), respectively; P < 0.05). Most patients would achieve plasma PK/pharmacodynamic (PD) targets of 90% for non-parapsilosis Candida spp. and C. parapsilosis with MICs of 0.008 and 0.064 mg/liter, respectively, for doses of 100 mg daily and 150 mg daily. The PKs of micafungin were not significantly different between burn patients and intra-abdominal infection patients. After the first dose, micafungin at 100 mg/day achieved the PK/PD targets in plasma for MIC values of ≤0.008 mg/liter and ≤0.064 mg/liter for non-parapsilosis Candida spp. and Candida parapsilosis species, respectively.

Micafungin versus anidulafungin in critically ill patients with invasive candidiasis: a retrospective study

Background

In critically ill patients the incidence of invasive fungal infections caused by Candida spp. has increased remarkably. Echinocandins are recommended as initial treatment for invasive fungal infections. The safety and efficacy of micafungin compared to caspofungin is similar, but no comparison is made between anidulafungin and micafungin concerning safety and efficacy. We therefore performed a retrospective study to assess these aspects in critically ill patients with invasive candidiasis.

Methods

All patients in the intensive care unit (ICU) with invasive candidiasis, who were only treated with anidulafungin or micafungin, between January 2012 and December 2014 were retrospectively included. Baseline demographic characteristics, infection characteristics and patient courses were assessed.

Results

A total of 63 patients received either anidulafungin (n = 30) or micafungin (n = 33) at the discretion of the attending intensivist. Baseline characteristics were comparable between the two groups, suggesting similar risk for developing invasive candidiasis. Patients with invasive candidiasis and liver failure were more often treated with anidulafungin than micafungin. Response rates were similar for both groups. No difference was observed in 28-day mortality, but 90-day mortality was higher in patients on anidulafungin. Multivariable cox regression analysis showed that age and serum bilirubin were the best parameters for the prediction of 90-day mortality, whereas APACHE II, Candida score and antifungal therapy did not contribute (P > 0.05). None of the patients developed impaired liver function related to antifungal use and no differences were seen in prothrombin time, serum transaminases and bilirubin levels between the groups, after exclusion of patients with liver injury or failure.

Conclusion

Micafungin can be safely and effectively used in critically ill patients with invasive candidiasis. The observed increased 90-day mortality with anidulafungin can be explained by intensivists unnecessarily avoiding micafungin in patients with liver injury and failure.

Prediction of micafungin area under the curve data by using peak concentration: applicability and utility in antifungal therapy

Aim: To describe a predictive model to obtain the area under the plasma concentration versus time curve (AUC) for micafungin to aid in dosing strategies in pediatric patients. Methods: Using published pharmacokinetic data a linear regression model to describe the Cmax versus AUCtau was developed. The mean absolute error prediction, root mean square error prediction along with correlation coefficient (r) and fold prediction criteria were used to evaluate the developed linear regression model for micafungin. Results: The predicted AUC for micafungin were contained within 0.5–1.5 fold difference. The mean absolute error and root mean square error for the developed model was 15 and 27%, respectively. Conclusion: The model may be used in a prospective manner for dosing decisions of micafungin in pediatric patients.

Pharmacokinetic/pharmacodynamic adequacy of echinocandins against Candida spp. in intensive care unit patients and general patient populations

This study evaluated whether contemporary echinocandin regimens achieved pharmacokinetic/pharmacodynamic targets in ICU patients and general patient populations (GPPs) and assessed caspofungin (CAS) regimens in hepatic impairment (HI) patients. A Monte Carlo simulation was performed using previously published data. Recommended dosing regimens of echinocandins in ICU patients, GPPs and healthy volunteers were evaluated: 70mg loading dose then 50mg maintenance dose (70/50mg) for CAS; 100mg q24h for micafungin (MCF); and 200/100mg for anidulafungin (ANF). Moreover, CAS 70mg and 100mg q24h in GPPs, and CAS 70/50mg and 70/35mg in mild and moderate HI patients, respectively, were evaluated. Cumulative fraction of response (CFR) was calculated for each dosing regimen. For Candida albicans, CFRs for the recommended doses of CAS, MCF and ANF were 95.8%, 13.5% and 50.5% in ICU patients and 96.3%, 42.4% and 61.6% in GPPs, respectively; for Candida glabrata, CFRs were 99.4%, 90.6% and 44.6% in ICU patients and 99.5%, 97.1% and 59.8% in GPPs. For Candida parapsilosis, CFRs of echinocandins for standard regimens were <70%; only CAS 100mg q24h achieved the target CFR. CAS 70/50mg and 70/35mg in mild and moderate HI patients were appropriate. Considerable interindividual variability was observed. For C. albicans and C. glabrata, CAS is good choice both for ICU and other patient populations, but for C. parapsilosis an increased dose should be considered. For MCF and ANF, administering higher doses with longer dosing intervals achieves better target attainment and should be investigated in clinical trials.