Pharmacokinetics of Anidulafungin in Obese and Normal-Weight Adults

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.

Candidemia in Adult Patients in the ICU: A Reappraisal of Susceptibility Testing and Antifungal Therapy

OBJECTIVE

To provide updates on the epidemiology and recommendations for management of candidemia in patients with critical illness.

DATA SOURCES

A literature search using the PubMed database (inception to March 2023) was conducted using the search terms "invasive candidiasis," "candidemia," "critically ill," "azoles," "echinocandin," "antifungal agents," "rapid diagnostics," "antifungal susceptibility testing," "therapeutic drug monitoring," "antifungal dosing," "persistent candidemia," and "Candida biofilm."

STUDY SELECTION/DATA EXTRACTION

Clinical data were limited to those published in the English language. Ongoing trials were identified through ClinicalTrials.gov.

DATA SYNTHESIS

A total of 109 articles were reviewed including 25 pharmacokinetic/pharmacodynamic studies and 30 studies including patient data, 13 of which were randomized controlled clinical trials. The remaining 54 articles included fungal surveillance data, in vitro studies, review articles, and survey data. The current 2016 Infectious Diseases Society of America (IDSA) Clinical Practice Guideline for the Management of Candidiasis provides recommendations for selecting empiric and definitive antifungal therapies for candidemia, but data are limited regarding optimized dosing strategies in critically ill patients with dynamic pharmacokinetic changes or persistent candidemia complicated.

RELEVANCE TO PATIENT CARE AND CLINICAL PRACTICE

Outcomes due to candidemia remain poor despite improved diagnostic platforms, antifungal susceptibility testing, and antifungal therapy selection for candidemia in critically ill patients. Earlier detection and identification of the species causing candidemia combined with recognition of patient-specific factors leading to dosing discrepancies are crucial to improving outcomes in critically ill patients with candidemia.

CONCLUSIONS

Treatment of candidemia in critically ill patients must account for the incidence of non-albicans Candida species and trends in antifungal resistance as well as overcome the complex pathophysiologic changes to avoid suboptimal antifungal exposure.

Patients with Obesity Should be Recognised as a Special Patient Population During Drug Development of Antibacterial and Antifungal Agents; A Call to Action

Individuals with obesity are at increased risk of developing infectious diseases. Timely administration of an effective dose of an antimicrobial agent is paramount to safeguard optimal therapy. For this purpose, special patient populations at risk for altered exposure such as renal or hepatic impairment are studied during drug development. Strikingly, there is no such evaluation in individuals with obesity despite a potential influence on exposure and a global obesity prevalence of 13 %. Optimal clinical decision making in patients with obesity is impossible without prior study of the drug of interest in this population. This statement is strengthened by an evaluation of 19 antimicrobial agents that showed tremendous variability in the influence of weight on clearance. In contrast to patient with renal or hepatic impairment who are mainly at risk of overexposure, individuals with obesity can be at risk of both under- and overexposure. Gaining knowledge on the influence of body weight on clearance during early phases of drug development may allow for optimisation of other phases of research, potentially increasing success rate of the drug, and can provide clinicians with vital information as soon as the drug reaches the market. Antimicrobial therapy should be tailored to obesity-related (patho)physiological changes and to reach this goal, obese individuals should be studied during drug development.

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.

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.

The Importance of Assessing Drug Pharmacokinetics and Pharmacodynamics in the Obese Population During Drug Development

Obesity remains a US national health crisis and a growing concern worldwide. Concerningly, individuals who are obese are at an increased risk for comorbid diseases that include, but are not limited to, hypertension, diabetes, cardiovascular disease, and cancer. Beyond the risk for developing these conditions, obesity may also impact the pharmacological activity of the therapies being used to treat them and other disease states. The pharmacokinetics (PK), pharmacodynamics (PD), safety, and efficacy of therapies, both currently marketed and under clinical development, may be directly impacted by the physiological alterations that occur secondary to the occurrence of chronic excess body weight. The increased prevalence of this disease should not be ignored. Both private and federal institutions involved in drug research and development should consider, as appropriate, a greater inclusion of individuals who are obese in clinical trials throughout the entirety of drug development, and leverage the available PK, PD, safety, and efficacy data to make more informed dosing recommendations.

Therapeutic Drug Monitoring of Antimicrobials in Critically Ill Obese Patients

Obesity is a significant global public health concern that is associated with an elevated risk of comorbidities as well as severe postoperative and nosocomial infections. The treatment of infections in critically ill obese patients can be challenging because obesity affects the pharmacokinetics and pharmacodynamics of antibiotics, leading to an increased risk of antibiotic therapy failure and toxicity due to inappropriate dosages. Precision dosing of antibiotics using therapeutic drug monitoring may help to improve the management of this patient population. This narrative review outlines the pharmacokinetic and pharmacodynamic changes that result from obesity and provides a comprehensive critical review of the current available data on dosage adjustment of antibiotics in critically ill obese patients.

Drug pharmacokinetics in the obese population: challenging common assumptions on predictors of obesity-related parameter changes

INTRODUCTION

Obesity is associated with many physiological changes. We review available evidence regarding five commonly accepted assumptions to a priori predict the impact of obesity on drug pharmacokinetics (PK).

AREAS COVERED

The investigated assumptions are: 1) lean body weight is the preferred descriptor of clearance and dose adjustments; 2) volume of distribution increases for lipophilic, but not for hydrophilic drugs; 3) CYP-3A4 activity is suppressed and UGT activity is increased, implying decreased and increased dose requirements for substrates of these enzyme systems, respectively; 4) glomerular filtration rate is enhanced, necessitating higher doses for drugs cleared through glomerular filtration; 5) drug dosing information from obese adults can be extrapolated to obese adolescents.

EXPERT OPINION

Available literature contradicts, or at least limits the generalizability, of all five assumptions. Clinical studies should focus on quantifying the impact of duration and severity of obesity on drug PK in adults and adolescents, and also include oral bioavailability and pharmacodynamics in these studies. Physiologically-based PK approaches can be used to predict PK changes for individual drugs, but can also be used to define in general terms based on patient characteristics and drug properties, when certain assumptions can or cannot be expected to be systematically accurate.

Effect of Laparoscopic Sleeve Gastrectomy on the Pharmacokinetics of Oral Omeprazole Using a Population Approach

Omeprazole is commonly prescribed to obese patients and patients after laparoscopic sleeve gastrectomy (LSG). The pharmacokinetics of oral omeprazole after LSG are still unknown. Therefore, the aim of this study was to investigate the pharmacokinetics of oral omeprazole in obese patients before and after LSG. A total of 331 blood samples were collected from 62 obese patients preoperatively (visit 1) followed by 41 patients 7 days post-LSG (visit 2) and 20 patients 1 month post-LSG (visit 3). Population pharmacokinetic analysis was performed using NONMEM to characterize the effect of LSG on omeprazole absorption and disposition. A one-compartment model with 12 transit absorption compartments and linear elimination successfully described the data. Compared with pre-surgery, the oral omeprazole time to maximum plasma concentration (T_max) was reduced and maximum plasma concentration (C_max) was higher, but the apparent clearance (CL/F) and area under the plasma concentration–time curve (AUC) were unchanged 7 days and 1 month after surgery. In addition, the CYP2C19 genotype and liver function exhibited a significant influence on omeprazole CL/F. LSG increased the rate of omeprazole absorption but did not affect omeprazole exposure. A dose of 20 mg omeprazole once daily may be adequate for relieving gastrointestinal tract discomfort at short-term follow-up post-LSG.

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.

Population pharmacokinetics of omeprazole in obese and normal-weight adults

BACKGROUND

Obesity is related to many pathophysiological changes that may result in altered drug disposition. Omeprazole is the most common option utilized for acid-related disorders treatment; however, the pharmacokinetic (PK) and dosing recommendations for the obese patient population are lacking.

METHODS

Data from 40 healthy subjects with normal weights and data from 61 obese subjects were included. The subjects all received a single dose of 20 mg of omeprazole. Nonlinear mixed effects modeling were performed to characterize the effect of obesity on omeprazole PK.

RESULTS

A one-compartment model with twelve transit absorption compartments and linear elimination described the data best. A lower clearance was observed in the obese patient population than in the normal-weight subjects, which was opposite to the well-known allometric effect of body weight on drug clearance. Moreover, the CYP2C19 genotype was identified as a significant covariate for clearance.

CONCLUSION

Given the potential adverse events related to high exposure to proton pump inhibitors over time, obese patients may require a lower dose of omeprazole for long-term treatment. Further studies in obese individuals into other drugs metabolized by CYP2C19 are warranted, especially those with a narrow therapeutic window.

CLINICAL TRIAL REGISTRATION

www.chictr.org.cn identifier is ChiCTR2100046578; www.chinadrugtrials.org.cn identifier is CTR20190175.

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.

Use and outcome of empiric echinocandins in critically ill patients

BACKGROUND

Echinocandins are recommended as a first-line empiric treatment for fungal infections of patients in an intensive care unit (ICU) with critical illness. The primary aim of the study was to compare outcomes among ICU patients treated with empiric anidulafungin (ANI), caspofungin (CASPO), or micafungin (MICA).

METHODS

A retrospective cohort study in a mixed adult ICU. Patient demographics, reason for ICU admission, ICU risk scores and organ support therapies were analyzed. Outcome parameters included ICU and hospital stay, 30-day mortality and 1-year mortality.

RESULTS

Empiric echinocandin therapy was given to 367 patients (ANI; 73 patients, CASPO; 84 patients, and MICA; 210 patients) with a median duration of 3 days in an ICU. Patient median age was 60.7 years. As a first-line therapy, 52% of patients received fluconazole. Positive Candida cultures were found in the following samples: blood, 16 (4.4%); central line, 27 (7.4%); deep site, 92 (25.1%). Median ICU stay (ANI 6.4 days, CASPO 5.3 days, MICA 8.1 days), hospital stay (ANI 33 days, CASPO 30 days, MICA 30 days), 30-day mortality (ANI 27%, CASPO 32%, MICA 32%), and 1-year mortality (ANI 33%, CASPO 44%, MICA 45%) did not differ between the groups . The cost of antifungal therapy during the ICU period was similar in the three echinocandin groups (ANI; €1 872, CASPO; €1 799, and MICA; €1783).

CONCLUSION

Our results show that ICU, hospital stay, and mortality (hospital, 30-day and 1-year) did not differ among patients with empiric anidulafungin, caspofungin, or micafungin treatment in a mixed adult ICU.

A Repurposed Drug Screen Identifies Compounds That Inhibit the Binding of the COVID-19 Spike Protein to ACE2

Repurposed drugs that block the interaction between the SARS-CoV-2 spike protein and its receptor ACE2 could offer a rapid route to novel COVID-19 treatments or prophylactics. Here, we screened 2,701 compounds from a commercial library of drugs approved by international regulatory agencies for their ability to inhibit the binding of recombinant, trimeric SARS-CoV-2 spike protein to recombinant human ACE2. We identified 56 compounds that inhibited binding in a concentration-dependent manner, measured the IC50 of binding inhibition, and computationally modeled the docking of the best inhibitors to the Spike-ACE2 binding interface. The best candidates were Thiostrepton, Oxytocin, Nilotinib, and Hydroxycamptothecin with IC50's in the 4-9 μM range. These results highlight an effective screening approach to identify compounds capable of disrupting the Spike-ACE2 interaction, as well as identify several potential inhibitors of the Spike-ACE2 interaction.

Antifungals in Clinical Use and the Pipeline

Over the past 15 years, there has been an increase in the development and utilization of newer antifungal agents. The ideal antifungal, however, in regard to spectrum of activity, pharmacokinetic/pharmacodynamic properties, development of resistance, safety, and drug interaction profile remains elusive. This article reviews pharmacologic aspects of Food and Drug Administration-approved polyenes, flucytosine, azoles, and echinocandins as well as promising pipeline antifungal agents. Unique properties of these newer agents are highlighted. The clinical role of established and investigational antifungal agents as treatment and/or prevention of invasive fungal infections is discussed.

A repurposed drug screen identifies compounds that inhibit the binding of the COVID-19 spike protein to ACE2

Repurposed drugs that block the interaction between the SARS-CoV-2 spike protein and its receptor ACE2 could offer a rapid route to novel COVID-19 treatments or prophylactics. Here, we screened 2701 compounds from a commercial library of drugs approved by international regulatory agencies for their ability to inhibit the binding of recombinant, trimeric SARS-CoV-2 spike protein to recombinant human ACE2. We identified 56 compounds that inhibited binding by <90%, measured the EC ₅₀ of binding inhibition, and computationally modeled the docking of the best inhibitors to both Spike and ACE2. These results highlight an effective screening approach to identify compounds capable of disrupting the Spike-ACE2 interaction as well as identifying several potential inhibitors that could serve as templates for future drug discovery efforts.

Rezafungin versus Caspofungin in a Phase 2, Randomized, Double-Blind Study for the Treatment of Candidemia and Invasive Candidiasis- The STRIVE Trial

Background

Rezafungin (RZF) is a novel echinocandin exhibiting distinctive pharmacokinetics/pharmacodynamics. STRIVE was a phase 2, double-blind, randomized trial designed to compare the safety and efficacy of RZF once weekly (QWk) to caspofungin (CAS) once daily for treatment of candidemia and/or invasive candidiasis (IC).

Methods

Adults with systemic signs and mycological confirmation of candidemia and/or IC were randomized to RZF 400 mg QWk (400 mg), RZF 400 mg on week 1 then 200 mg QWk (400/200 mg), or CAS 70 mg as a loading dose followed by 50 mg daily for ≤4 weeks. Efficacy assessments included overall cure (resolution of signs of candidemia/IC + mycological eradication) at day 14 (primary endpoint), investigator-assessed clinical response at day 14, and 30-day all-cause mortality (ACM) (secondary endpoints), and time to negative blood culture. Safety was evaluated by adverse events and ACM through follow-up.

Results

Of 207 patients enrolled, 183 were in the microbiological intent-to-treat population (~21% IC). Overall cure rates were 60.5% (46/76) for RZF 400 mg, 76.1% (35/46) for RZF 400/200 mg, and 67.2% (41/61) for CAS; investigator-assessed clinical cure rates were 69.7% (53/76), 80.4% (37/46), and 70.5% (43/61), respectively. In total, 30-day ACM was 15.8% for RZF 400 mg, 4.4% for RZF 400/200 mg, and 13.1% for CAS. Candidemia was cleared in 19.5 and 22.8 hours in RZF and CAS patients, respectively. No concerning safety trends were observed; ACM through follow-up was 15.2% (21/138) for RZF and 18.8% (13/69) for CAS.

Conclusions

RZF was safe and efficacious in the treatment of candidemia and/or IC.

Clinical Trials Registration

NCT02734862

Pharmacokinetics of echinocandins in suspected candida peritonitis: A potential risk for resistance

INTRODUCTION

A possible increase in Candida resistance, especially in Candida glabrata, has been speculated according to poor diffusion of echinocandins to peritoneal fluid.

MATERIALS/METHODS

Peritoneal and serum concentrations of caspofungin, micafungin and anidulafungin were analysed in surgical patients with suspected candida peritonitis. After 4 days of starting therapy, serum and peritoneal samples (through peritoneal drainage) were obtained at baseline, 1, 6, 12 and 24 h of drug administration. Micafungin and anidulafungin concentrations were determined using high-performance liquid chromatography (HPLC/F), whereas caspofungin concentrations were established by bioassay.

RESULTS

Twenty-three critically ill patients with suspected abdominal fungal infection who were receiving an echinocandin were prospectively recruited. No specific criteria were applied to prescribe one specific echinocandin. No special clinical differences were observed among the three groups of patients. All were receiving antibiotic therapy, 80% required inotropic drugs, and fungal peritonitis was confirmed in 74% of them. The AUC_{0_24h} (mg × h/L) obtained in serum and peritoneal fluid were: 126.84 and 34.38, 98.52 and 18.83, and 66.9 and 8.78 for anidulafungin, micafungin and caspofungin, respectively. The median concentration in peritoneal fluid ranged from 0.66 to 1.82 μg/mL for anidulafungin, 0.68-0.88 μg/mL for micafungin and 0.21-0.46 μg/mL for caspofungin.

CONCLUSION

The results showed moderate penetration of echinocandins into the peritoneal fluid of these patients. These levels are below the threshold of resistance mutant selection published by other authors. This could justify a potential risk of resistance in patients with prolonged treatment with echinocandins and suboptimal control of abdominal infection.

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.

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.

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.