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/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.

Anidulafungin exposure and population pharmacokinetics in critically ill patients with invasive candidiasis

PURPOSE

Anidulafungin is recommended as a first-line treatment for invasive Candida infections in critically ill patients. Pharmacokinetic (PK) variability is large in critically ill patients, potentially compromising pharmacokinetic-pharmacodynamic (PKPD) target attainment under standard dosing. We aimed to assess anidulafungin exposure, PKPD target attainment, and population (pop)PK in critically ill patients.

METHODS

Adult ICU patients receiving standard anidulafungin dosing [200 mg on day 1, then 100 mg daily] were included (NCT04045366). We performed rich blood sampling on an early (day 2 ± 1) and/or late (day 5 ± 1) treatment day. Using total anidulafungin plasma concentrations, we developed a popPK model (NONMEM7.5) and conducted Monte Carlo simulations (n = 1,000 per virtual patient) to evaluate the impact of patient factors on PKPD target attainment (AUC24h target 83.5 mg×h/L).

RESULTS

Twenty patients contributed 188 anidulafungin concentrations. PKPD target attainment was 45% and 65% on early and late sampling days, respectively. A two-compartment popPK model with first-order elimination described the data. Anidulafungin clearance increased with bodyweight and central volume of distribution increased as serum albumin decreased. Both bodyweight and serum albumin had a clinically relevant impact on PKPD target attainment at day 1 (area under the ROC curve; AUROC 0.82 and 0.62, respectively), and bodyweight on PKPD target attainment at day 14 (AUROC 0.94). Standard anidulafungin dosing regimen fails to achieve adequate target attainment throughout the treatment period.

CONCLUSION

Standard anidulafungin dosing is insufficient for achieving adequate exposure in critically ill patients. An interactive simulation tool is provided to aid dose-finding research and explore different dosing strategies and targets.

Echinocandins Pharmacokinetics: A Comprehensive Review of Micafungin, Caspofungin, Anidulafungin, and Rezafungin Population Pharmacokinetic Models and Dose Optimization in Special Populations

In recent years, many population pharmacokinetic (popPK) models have been developed for echinocandins to better understand the pharmacokinetics (PK) of these antifungals. This comprehensive review aimed to summarize popPK models of echinocandins (micafungin, caspofungin, anidulafungin, and rezafungin), by focusing on dosage optimization to maximize the probability of attaining the PK/PD target proposed in special populations. A search in PubMed, Embase, Web of Science, and Scopus, supplemented by the bibliography of relevant articles, was conducted from inception to March 2024, including both observational and prospective trials. A total of 1126 articles were identified, 47 of them were included in the review (22 for micafungin, 13 for caspofungin, 9 for anidulafungin, and 3 for rezafungin). A two-compartment model was more frequently used to describe the PK parameters of echinocandin (78.7% of developed models), although more complex structural models with three and four compartments have also been developed. The covariates to estimate the PK parameters such as clearance (CL) and volume of distribution (Vd) differed between models. Weight total (WT) was the most frequently reported to be a significant predictor for both parameters, especially for estimating the CL in pediatrics. The PD parameter most widely reported assessing the drug exposure-efficacy relationship was the area under the concentration-time curve to minimum inhibitory concentration (MIC) ratio (AUC0-24/MIC) with different targets proposed for each echinocandin. In certain populations such as patients that are critically ill, obese, receiving extracorporeal membrane oxygenation (ECMO) and/or continuous renal replacement therapy (CRRT), or pediatric patients and/or patients with cancer or that are immunocompromised, the fixed dosing strategies recommended in the drug prescribing information may not reach the PK/PD target. For these populations, different strategies have been proposed, such as a dosing regimen based on body weight or increasing the loading and/or maintenance dose. Despite echinocandins' favorable safety profile and predictable PK, certain groups at risk of suboptimal drug exposure can benefit from therapeutic drug monitoring (TDM) to prevent clinical failures. Numerous popPK models of echinocandins have been developed. However, an external validation of the suggested dosing regimens in conjunction with an analysis of population subgroups should be conducted before implementing a popPK model in clinical practice.