Anidulafungin Dosing on VV ECMO
Use standard anidulafungin dosing (200 mg loading dose, then 100 mg daily) for patients on VV ECMO, as the drug's pharmacokinetics are minimally affected by extracorporeal circuits, though therapeutic drug monitoring should be strongly considered to ensure adequate exposure. 1, 2
Rationale for Standard Dosing
Anidulafungin undergoes chemical degradation rather than hepatic or renal metabolism, making it less susceptible to the pharmacokinetic alterations typically seen in critically ill patients on ECMO 2
The drug is not dialyzable and has negligible renal clearance (clearance approximately 1 L/h), with a terminal elimination half-life of 40-50 hours that remains stable across various patient populations 2
Current evidence suggests that standard dosing regimens derived from critically ill patients not on ECMO are reasonable for ECMO patients, given insufficient data to provide definitive alternative dosing guidance 3
Standard Dosing Regimen
Loading dose: 200 mg IV on day 1 4
Maintenance dose: 100 mg IV daily starting on day 2 4
Infusion rate: 1 mg/min to minimize infusion-related reactions 2
Critical Consideration: Therapeutic Drug Monitoring
Therapeutic drug monitoring (TDM) is strongly recommended for echinocandins in critically ill patients on extracorporeal circuits due to risk of altered drug exposures. 1
Target trough concentration (Cmin): >1 mg/L to provide acceptable exposure based on current MIC distributions 1
TDM is particularly important in patients with:
High pharmacokinetic variability in ECMO patients necessitates individualized monitoring to prevent subtherapeutic or toxic exposures 3
ECMO-Specific Considerations
Data on echinocandins in ECMO are limited and inconsistent, with varied reports of concentration loss in ECMO circuits 5, 3
Volume of distribution may be increased in ECMO patients (anidulafungin Vd is 30-50 L, similar to total body fluid volume), potentially requiring higher initial doses in some cases 2, 3
Recent evidence suggests echinocandins are preferred for invasive candidiasis in ECMO patients, though choosing among them remains challenging due to limited data 5
The 2024 review on antifungals in ECMO notes that echinocandins have uncertain concentration losses in circuits, warranting caution and monitoring 5
Common Pitfalls to Avoid
Do not assume standard dosing is always adequate – the critically ill ECMO population has unpredictable pharmacokinetics requiring verification through TDM 1, 3
Do not delay TDM until treatment failure occurs – proactive monitoring near therapy initiation or after circuit changes is essential 6
Do not overlook hypoalbuminemia – severe protein depletion can significantly alter free drug concentrations despite total plasma levels appearing adequate 1
Avoid empiric dose escalation without TDM data – while higher doses may be needed, this should be guided by measured concentrations rather than assumptions 3, 7
Alternative Echinocandin Options
If anidulafungin is unavailable or TDM suggests inadequate exposure:
Caspofungin: 70 mg loading dose, then 50 mg daily (may require higher maintenance doses of 70-100 mg in ECMO patients based on recent PK data) 4, 8
Micafungin: 100 mg daily (no loading dose required) 4
Recent population PK modeling in ECMO patients suggests higher-than-standard empirical dosing (e.g., caspofungin 100 mg loading, then 100 mg daily) may be advantageous 8