Population pharmacokinetic-pharmacodynamic analysis of anidulafungin in adult patients with fungal infections

Evaluation of clinical outcomes of anidulafungin for the treatment of candidemia in hospitalized critically ill patients with obesity: A multicenter, retrospective cohort study

OBJECTIVES

To evaluate the clinical outcomes of anidulafungin for candidemia treatment in critically ill patients with obesity.

METHODS

A multicenter, retrospective cohort study was conducted in Saudi Arabia for critically ill adults with candidemia who received anidulafungin. Patients with obesity have a body mass index ≥30 kg/m2. The primary outcome was the clinical cure rate.

RESULTS

A total of 146 patients were included, 64 of whom were obese. There were no statistically significant differences in the clinical cure rate (P = 0.63), microbiological cure rate (P = 0.27), or the median time for a clinical cure (P = 0.13) for patients with obesity compared to non-obese patients. The median time for a microbiological cure was longer in non-obese patients than in patients with obesity (P = 0.04). The median hospital length of stay and the median mechanical ventilation durations were numerically longer in patients with obesity.

CONCLUSIONS

Clinical and microbiological cure rates and time for clinical cure were statistically similar for both groups. Considering the study's limitations (especially with a small sample size), it is uncertain if patients with obesity have similar effectiveness to non-obese patients. Future studies with larger sample sizes are warranted to evaluate if obesity negatively impacts anidulafungin's clinical outcomes for candidemia.

Drug dosing in obese critically ill patients, a literature review

INTRODUCTION

The prevalence of obesity represents a significant global public health challenge, and the available evidence concerning the appropriate dosing of pharmaceutical in patients with obesity is limited. It is uncommon for clinical trials in critically ill patients to include obese individuals, which results in a lack of specific dosing information in product data sheets. The objective of this literature review is to provide clinicians with efficacious and secure guidelines for this cohort of patients.

METHODS

A multidisciplinary team comprising pharmacists specialized in hospital pharmacy and physicians with expertise in intensive care medicine was established. The therapeutic groups and, in particular, the most commonly used active ingredients within the Intensive Care Unit were identified and subjected to detailed analysis. The following terms were included in the search: "obese", "overweight", "critical illness", "drug dosification", and "therapeutic dose monitoring". All the information was then evaluated by the working group, which reached a consensus on the dosing recommendations for each drug in obese critically ill patients.

RESULTS

A total of 83 drugs belonging to the following therapeutic groups were identified: antivirals, antibacterials, antifungals, immunosuppressants, antiepileptics, vasopressors, anticoagulants, neuromuscular blocking agents and sedatives. A table was produced containing the consensus dosing recommendations for each of the aforementioned drugs following a review of the available evidence.

CONCLUSIONS

Drug dosing in obese patients, both in critical and noncritical settings, remains an area with significant uncertainty. This review provides comprehensive and up-to-date information on the dosing of the main therapeutic groups in obese critically ill patients, offering a valuable resource physicians in critical care units and clinical pharmacists in their practice in this setting.

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.

Anidulafungin Levels in Breast Milk After Cessation of Treatment: A Case Report

Background: Anidulafungin has poor oral bioavailability, with hardly any available information on how it affects breast milk, oral absorption, or gastrointestinal side effects in the infant. Case Presentation: A 40-year-old woman who recently gave birth to a healthy infant was treated for a period of 14 days for a Candida glabrata with 100 mg anidulafungin once a day. The department of clinical pharmacy was consulted to provide advice on how long the patient had to wait after ceasing anidulafungin before it was safe to start breastfeeding, with regard to preventing possible side effects of the drug to the infant, such as diarrhea or cholestasis and increase in liver enzyme values. The advice of the hospital pharmacist was pragmatic: to start breastfeeding within 2 days after the medication was discontinued based on half-time. Results: Owing to this lack of information, we measured anidulafungin concentrations in breast milk and found low levels. Conclusion: We concluded that anidulafungin is detectable in breast milk until 32 hours after anidulafungin treatment was stopped, and that no side effects were observed by the infant.

Optimizing anidulafungin exposure across a wide adult body size range

Echinocandins like anidulafungin are first-line therapies for candidemia and invasive candidiasis, but their dosing may be suboptimal in obese patients. Our objective was to quantify anidulafungin exposure in a cohort of adults across a wide body size range to test if body size affects anidulafungin pharmacokinetics (PK). We enrolled 20 adults between the ages of 18 and 80 years, with an equal distribution of patients above and below a body mass index of 30 kg/m2. A single 100-mg dose of anidulafungin was administered, followed by intensive sampling over 72 h. Population PK analysis was used to identify and compare covariates of anidulafungin PK parameters. Monte Carlo simulations were performed to compute the probability of target attainment (PTA) based on alternative dosing regimens. Participants (45% males) had a median (range) age of 45 (21-78) years and a median (range) weight of 82.7 (42.4-208.3) kg. The observed median (range) of AUC0-∞ was 106.4 (51.9, 138.4) mg∙h/L. Lean body weight (LBW) and adjusted body weight (AdjBW) were more influential than weight as covariates of anidulafungin PK parameters. The conventional 100 mg daily maintenance is predicted to have a PTA below 90% in adults with an LBW > 55 kg or an AdjBW > 75 kg. A daily maintenance dose of 150-200 mg is predicted in these heavier adults. Anidulafungin AUC0-∞ declines with increasing body size. A higher maintenance dose will increase the PTA compared to the current approach in obese patients.

Therapeutic Drug Monitoring of Antifungal Agents in Critically Ill Patients: Is There a Need for Dose Optimisation?

Invasive fungal infections are an important cause of morbidity and mortality, especially in critically ill patients. Increasing resistance rates and inadequate antifungal exposure have been documented in these patients, due to clinically relevant pharmacokinetic (PK) and pharmacodynamic (PD) alterations, leading to treatment failure. Physiological changes such as third spacing (movement of fluid from the intravascular compartment to the interstitial space), hypoalbuminemia, renal failure and hepatic failure, as well as common interventions in the intensive care unit, such as renal replacement therapy and extracorporeal membrane oxygenation, can lead to these PK and PD alterations. Consequently, a therapeutic target concentration that may be useful for one patient may not be appropriate for another. Regular doses do not take into account the important PK variations in the critically ill, and the need to select an effective dose while minimising toxicity advocates for the use of therapeutic drug monitoring (TDM). This review aims to describe the current evidence regarding optimal PK/PD indices associated with the clinical efficacy of the most commonly used antifungal agents in critically ill patients (azoles, echinocandins, lipid complexes of amphotericin B, and flucytosine), provide a comprehensive understanding of the factors affecting the PK of each agent, document the PK parameters of critically ill patients compared to healthy volunteers, and, finally, make recommendations for therapeutic drug monitoring (TDM) of antifungals in critically ill patients.

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.

Methodological features of clinical pharmacokinetic-pharmacodynamic studies of antibacterials and antifungals: a systematic review

BACKGROUND

Pharmacokinetic (PK)-pharmacodynamic (PD) indices relate measures of drug exposure to antibacterial effect. Clinical PK-PD studies aim to correlate PK-PD indices with outcomes in patients. Optimization of dosing based on pre-clinical studies means that PK-PD relationships are difficult to establish; therefore studies need to be designed and reported carefully to validate pre-clinical findings.

OBJECTIVES

To describe the methodological features of clinical antibacterial and antifungal PK-PD studies that reported the relationship between PK-PD indices and clinical or microbiological responses.

METHODS

Studies published between 1980 and 2015 were identified through systematic searches. Methodological features of eligible studies were extracted.

RESULTS

We identified 85 publications containing 97 PK-PD analyses. Most studies were small, with fewer than 100 patients. Around a quarter were performed on patients with infections due to a single specific pathogen. In approximately one-third of studies, patients received concurrent antibiotics/antifungals and in some other studies patients received other treatments that may confound the PK-PD-outcome relationship. Most studies measured antimicrobial concentrations in blood/serum and only four measured free concentrations. Most performed some form of regression, time-to-event analysis or used the Hill/Emax equation to examine the association between PK-PD index and outcome. Target values of PK-PD indices that predict outcomes were investigated in 52% of studies. Target identification was most commonly done using recursive partitioning or logistic regression.

CONCLUSIONS

Given the variability in conduct and reporting, we suggest that an agreed set of standards for the conduct and reporting of studies should be developed.

Population pharmacokinetics of anidulafungin in ICU patients assessing inter- and intrasubject variability

AIMS

The population pharmacokinetics (PK) of anidulafungin in critically ill patients hospitalized in intensive care units (ICUs) was explored with the intention of evaluating and optimizing dosing regimens.

METHODS

A PK study was conducted in a cohort of 13 patients treated with anidulafungin using intensive sampling during multiple periods per patient and the high-performance liquid chromatography method for drug quantification. A population PK model was developed to describe the concentration-time course of anidulafungin and the inter-individual (IIV) and interoccasion variability (IOV) of the PK parameters. Model-based PK simulations have been performed to estimate the probability of target attainment (PTA), given the pharmacokinetic/pharmacodynamic target of free 24-hour area under the free drug concentration-time curve over minimum inhibitory concentration for several dosing regimens.

RESULTS

A two-compartment PK model, with first-order elimination, best described the data with population clearance (CL) and central/peripheral volume of distribution (V1/V2) of 0.778 L/h and 10.2/21.1 L, respectively, and a mean ± s.d. AUC_0-24 of 119.97 ± 46.23 mg·h/L. Pronounced IIV and IOV variability was found for CL (38% and 31%) and V1 (47% and 30%), respectively. Sequential Organ Failure Assessment (SOFA) and Body Mass Index (BMI) were found to be covariates on CL and V1, respectively. Low PTA values were calculated for borderline Clinical & Laboratory Standards Institute (CLSI)-susceptible Candida strains.

CONCLUSIONS

Although anidulafungin exposure was found comparable to that in healthy volunteers, elevated interindividual and significant interoccasion variability was found in critically ill ICU patients, which resulted in reduced PTA values in these patients.

Population Analysis of Anidulafungin in Infants to Older Adults With Confirmed or Suspected Invasive Candidiasis

In a pooled population analysis, we investigated the pharmacokinetics of i.v. anidulafungin in four studies across a full range of adult and pediatric ages in patients with confirmed, suspected, or at high risk of invasive candidiasis (IC). Relationships between anidulafungin exposure and key efficacy end points (global response of success and all‐cause mortality) and safety end points (all‐cause hepatic or gastrointestinal adverse events) in all patients and separately in pediatric patients and the appropriate dosing regimen for IC treatment in pediatric patients were evaluated. Pediatric patients received a 3.0 mg/kg (maximum 200 mg) i.v. loading dose and 1.5 mg/kg (maximum 100 mg) daily thereafter. Adults received a 200 mg i.v. loading dose and 100 mg daily thereafter. Estimated systemic anidulafungin exposures were similar across age groups (neonates to adults) at the weight‐based doses studied in pediatric patients. No clear associations were identified between anidulafungin exposure and efficacy or safety end points.

Population Pharmacokinetics of Anidulafungin in Critically Ill Patients

A two-compartment pharmacokinetic (PK) population model of anidulafungin was fitted to PK data from 23 critically ill patients (age, 65 years [range, 28 to 81 years]; total body weight [TBW], 75 kg [range, 54 to 168 kg]). TBW was associated with clearance and incorporated into a final population PK model. Simulations suggested that patients with higher TBWs had less-extensive MIC coverage. Dosage escalation may be warranted in patients with high TBWs to ensure optimal drug exposures for treatment of Candida albicans and Candida glabrata infections.

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.

Pharmacokinetic study of anidulafungin in ICU patients with intra-abdominal candidiasis

Background

Only limited pharmacokinetic data are available for anidulafungin in ICU patients, especially in patients treated for severe intra-abdominal infection (IAI).

Methods

This was a prospective multicentre observational study in ICU patients with suspected yeast IAI. All patients received an intravenous loading dose of 200 mg of anidulafungin, followed by 100 mg/day. Thirteen blood samples were drawn between day 1 and day 5 for pharmacokinetic analysis. Samples were analysed by an HPLC-tandem MS method. Demographics and SAPS2 and SOFA scores were recorded.

Results

Fourteen patients with a median age (IQR) of 62 years (48-70) and with a mean BMI of 30.5 kg/m 2 were included from three centres; 57.1% were women. Their median (IQR) SAPS2 score was 54 (45-67) and their median (IQR) SOFA score was 8 (7-12). Six patients with community-acquired IAI and eight patients with nosocomial-acquired IAI were included. Twelve yeasts were isolated: six Candida albicans , two Candida glabrata , two Candida tropicalis , one Candida parapsilosis and one Candida krusei . Pharmacokinetic parameters were as follows [mean (% coefficient of variation)]: C max (mg/L) = 6.0 (29%); T max (h) = 1.6 (25.8%); C min (mg/L) = 3.2 (36.8%); AUC 0-24 (mg·h/L) = 88.9 (38.6%); t 1/2 (h) = 42.1 (68.2%); CL (L/h) = 1.2 (42.3%); and V (L) = 72.8 (87.8%). A two-compartment model best described the anidulafungin concentrations in the population pharmacokinetic study.

Conclusions

The pharmacokinetic parameters of anidulafungin in critically ill ICU patients with complicated IAI are similar to those observed in the literature. However, an increased V and a longer t 1/2 were observed in this study. (EudraCT No. 2010-018695-25).

Does Weight Impact Anidulafungin Pharmacokinetics?

Bodyweight has been shown to influence anidulafungin exposure, but data from obese patients are lacking. We determined anidulafungin pharmacokinetics (100-mg single dose) in eight morbidly obese subjects (body mass index >40 kg/m(2)). Anidulafungin exposure was on average 32.5 % lower compared with the general patient population, suggesting dose increases may be required in this population.

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.).

Dose optimization of voriconazole/anidulafungin combination against Aspergillus fumigatus using an in vitro pharmacokinetic/pharmacodynamic model and response surface analysis: clinical implications for azole-resistant aspergillosis

BACKGROUND

Combination therapy of voriconazole with an echinocandin is often employed in order to increase the efficacy of voriconazole monotherapy.

METHODS

Four clinical Aspergillus fumigatus isolates with different in vitro susceptibilities to voriconazole (MIC 0.125-2 mg/L) and anidulafungin (MEC 0.008-0.016 mg/L) were tested in an in vitro pharmacokinetic/pharmacodynamic model simulating human serum concentrations of standard dosages of voriconazole and anidulafungin. Fungal growth was assessed using galactomannan production and quantitative PCR. Drug concentrations were determined with bioassays. Pharmacodynamic interactions were assessed using Bliss independence analysis (BI) and Loewe additivity-based canonical mixture response-surface non-linear regression analysis (LA). Probability of target attainment (PTA) was estimated with Monte Carlo analysis for different doses of anidulafungin (25, 50 and 100 mg) and azole resistance rates (5%-25%).

RESULTS

Synergy [BI 51% (8%-80%), LA 0.63 (0.38-0.79)] was found at low anidulafungin (fC_max/MEC <10) and voriconazole (fAUC/MIC <10) exposures, whereas antagonism [BI 12% (5%-18%, LA 1.12 (1.04-4.6)] was found at higher drug exposures. The largest increase in PTA was found with 25 mg of anidulafungin and voriconazole MIC distributions with high (>10%) resistance rates. PTAs for isolates with voriconazole MICs of 1, 2 and 4 mg/L was 78%, 12% and 0% with voriconazole monotherapy and 96%-100%, 68%-82% and 9%-20% with combination therapy, respectively. Optimal activity was associated with a voriconazole tC_min/MIC ratio of 1.5 for monotherapy and 0.75 for combination therapy.

CONCLUSIONS

The present study indicated that the combination of voriconazole with low-dose anidulafungin may increase the efficacy and reduce the cost and potential toxicity of antifungal therapy, particularly against azole-resistant A. fumigatus isolates and in patients with subtherapeutic serum levels. This hypothesis warrants further in vivo verification.

Azole-resistant Candida albicans prosthetic joint infection treated with prolonged administration of anidulafungin and two-stage exchange with implant of a mega-prosthesis

Fungal prosthetic joint infection (PJI) is a rare but severe complication of artroplasty. We report a case of PJI due to azole-resistant Candida albicans successfully treated with combination of prolonged administration of anidulafungin and two-stage joint exchange with insertion of a mega-prosthesis.

[Echinocandins: Applied pharmacology]

The echinocandins share pharmacodynamic properties, although there are some interesting differences in their pharmacokinetic behaviour in the clinical practice. They are not absorbed by the oral route. They have a somewhat special distribution in the organism, as some of them can reach high intracellular concentrations while, with some others, the concentration is reduced. They are highly bound to plasma proteins, thus it is recommended to administer a loading dose for anidulafungin and caspofungin, although this procedure is not yet clear with micafungin. Echinocandins are excreted via a non-microsomal metabolism, so the urinary concentration is very low. Some carrier proteins that take part in the biliary clearance process are probably involved in the interactions described with caspofungin and micafungin. These two drugs must be used with caution in patients with severely impaired hepatic function, while all of them can be used without special precautions when there is renal impairment or the patient requires renal replacement therapy.

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.

Impact of special patient populations on the pharmacokinetics of echinocandins

Echinocandins belong to the class of antifungal agents. Currently, three echinocandin drugs are licensed for intravenous treatment of invasive fungal infections: anidulafungin, caspofungin and micafungin. While their antifungal activity overlaps, there are substantial differences in pharmacokinetics (PK). Numerous factors may account for variability in PK of echinocandins including age (pediatrics vs adults), body surface area and body composition (normal weight vs obesity), disease status (e.g., critically ill and burn patients) and organ dysfunction (kidney and liver impairment). Subsequent effects of altered exposure might impact efficacy and safety. Knowledge of PK behavior is crucial in optimal clinical utilization of echinocandin in a specific patient or patient population. This review provides up-to-date information on PK data of anidulafungin, caspofungin and micafungin in special patient populations. Patient populations addressed are neonates, children and adolescents, obese patients, patients with hepatic or renal impairment, critically ill patients (including burn patients) and patients with hematological diseases.

A rationale for reduced-frequency dosing of anidulafungin for antifungal prophylaxis in immunocompromised patients

OBJECTIVES

Reduced-frequency dosing strategies of anidulafungin may offer a more convenient way of providing adequate antifungal prophylaxis to patients at high risk of invasive fungal diseases. We aimed to provide the pharmacological rationale for the applicability of reduced-frequency dosing regimens.

METHODS

We defined two groups of 10 patients that were to receive anidulafungin at 200 mg every 48 h or 300 mg every 72 h. Blood samples were drawn daily and two pharmacokinetic curves were constructed after 1 and 2 weeks of treatment. A population pharmacokinetic model was developed using non-linear mixed-effects modelling. ClinicalTrials.gov identifier: NCT01249820.

RESULTS

The AUC over a 6 day period (IQR) for a typical patient on 200 mg every 48 h or 300 mg every 72 h resulted in 348 mg · h/L (310.6-386.7) and 359 mg · h/L (319.1-400.9), respectively, comparable to the licensed regimen [397.0 mg · h/L (352.4-440.5)]. In the final model, the volume of distribution proved to be dependent on the lean body mass and CL of cyclosporine A. All three regimens resulted in comparable dose-normalized exposure over time.

CONCLUSIONS

We now have sufficient evidence to start using less frequent dosing regimens and demonstrate their value in clinical practice. These less frequently applied infusions enable more personalized care in an outpatient setting with reduced costs.

Comparison of the probability of target attainment of anidulafungin against Candida spp. in patients with acute leukaemia

This study aimed to investigate the probability of target attainment (PTA) of various anidulafungin dosing regimens against Candida spp. in patients with acute leukaemia. A Monte Carlo simulation was performed using a previously published population pharmacokinetic model. The following dosing scenarios were evaluated: 200 mg loading dose (LD) on Day 1 then 100 mg daily (manufacturer's recommended dosing regimen); 200 mg LD on Day 1 then 100 mg every 48 h (q48 h); and 200 mg q48 h, 200 mg every 72 h (q72 h) and 300 mg q72 h. For each dosing regimen, free drug concentrations were calculated to evaluate the effect of 99% protein binding. The PTA at various pharmacodynamic (PD) targets was determined as the percentage of subjects who achieved a free drug area under the plasma concentration-time curve over the minimum inhibitory concentration ratio (ƒAUC/MIC) or a free drug maximum plasma concentration over the minimum inhibitory concentration ratio (ƒC(max)/MIC) above the PD targets. PTA expectation values were then calculated for each dosing regimen. The currently recommended dosing regimen of anidulafungin was not optimal for invasive candidiasis in patients with acute leukaemia. Alternate dosing strategies with higher doses and extended dosing intervals (intermittent dosing) achieved better target attainment. This is the first study to optimise therapy with anidulafungin using Monte Carlo simulation. These results provide a rationale in support of future clinical investigation of intermittent dosing of anidulafungin.

Population pharmacokinetic analysis of voriconazole and anidulafungin in adult patients with invasive aspergillosis

To assess the pharmacokinetics (PK) of voriconazole and anidulafungin in patients with invasive aspergillosis (IA) in comparison with other populations, sparse PK data were obtained for 305 adults from a prospective phase 3 study comparing voriconazole and anidulafungin in combination versus voriconazole monotherapy (voriconazole, 6 mg/kg intravenously [IV] every 12 h [q12h] for 24 h followed by 4 mg/kg IV q12h, switched to 300 mg orally q12h as appropriate; with placebo or anidulafungin IV, a 200-mg loading dose followed by 100 mg q24h). Voriconazole PK was described by a two-compartment model with first-order absorption and mixed linear and time-dependent nonlinear (Michaelis-Menten) elimination; anidulafungin PK was described by a two-compartment model with first-order elimination. For voriconazole, the normal inverse Wishart prior approach was implemented to stabilize the model. Compared to previous models, no new covariates were identified for voriconazole or anidulafungin. PK parameter estimates of voriconazole and anidulafungin are in agreement with those reported previously except for voriconazole clearance (the nonlinear clearance component became minimal). At a 4-mg/kg IV dose, voriconazole exposure tended to increase slightly as age, weight, or body mass index increased, but the difference was not considered clinically relevant. Estimated voriconazole exposures in IA patients at 4 mg/kg IV were higher than those reported for healthy adults (e.g., the average area under the curve over a 12-hour dosing interval [AUC0-12] at steady state was 46% higher); while it is not definitive, age and concomitant medications may impact this difference. Estimated anidulafungin exposures in IA patients were comparable to those reported for the general patient population. This study was approved by the appropriate institutional review boards or ethics committees and registered on ClinicalTrials.gov (NCT00531479).

Pharmacokinetics of anidulafungin in critically ill patients with candidemia/invasive candidiasis

The pharmacokinetics of intravenous anidulafungin in adult intensive care unit (ICU) patients were assessed in this study and compared with historical data from a general patient population and healthy subjects. Intensive plasma sampling was performed over a dosing interval at steady state from 21 ICU patients with candidemia/invasive candidiasis. All patients received the recommended dosing regimen (a 200-mg loading dose on day 1, followed by a daily 100-mg maintenance dose), except for a 54-year-old 240-kg female patient (who received a daily 150-mg maintenance dose instead). Plasma samples were assayed for anidulafungin using a validated liquid chromatography-tandem mass spectrometry method. Pharmacokinetic parameters in ICU patients were calculated by a noncompartmental method. With the exclusion of the 240-kg patient, the median (minimum, maximum) age, weight, and body mass index (BMI) of 20 ICU patients were 57 (39, 78) years, 65 (48, 106) kg, and 23.3 (16.2, 33.8) kg/m(2), respectively. The average anidulafungin area under the curve over the 24-hour dosing interval (AUC(0-24)), maximum concentration (C(max)), and clearance (CL) in 20 ICU patients were 92.7 mg · h/liter, 7.7 mg/liter, and 1.3 liters/h, respectively. The exposure in the 240-kg patient at a daily 150-mg dose was within the range observed in ICU patients overall. The average AUC(0-24) and Cmax in the general patient population and healthy subjects were 110.3 and 105.9 mg · h/liter and 7.2 and 7.0 mg/liter, respectively. The pharmacokinetics of anidulafungin in ICU patients appeared to be comparable to those in the general patient population and healthy subjects at the same dosing regimen.