Antifungals Renal Dosing by Creatinine Clearance

This chart covers renal dose adjustment for the 3 antifungals in this registry: Amphotericin B, Fluconazole and Flucytosine. Of these, 2 are dosed by creatinine clearance from Cockcroft-Gault (Fluconazole and Flucytosine); and 1 has no CrCl dose band (Amphotericin B). Each drug links to its own page with the full threshold, cautions, and an FDA-label reference.

Reviewed and approved by Dr. Rishi Kumar Kafle, MBBS, MD, FASN. Always confirm against the label.

Antifungals: renal dosing chart

Cutoffs That Change Antifungals Doses

The rules above name 1 creatinine clearance cutoff. Each line lists the drugs whose rule changes at that value:

• 50 mL/min: Fluconazole

Rules without a numeric renal-function cutoff: Flucytosine and Amphotericin B. Read their full rule in the chart and on each drug page. A cutoff that sits between two bands still needs the label wording, because some labels use "less than" and others "at or below" the value.

Worked Example: Antifungals at a CrCl of About 49 mL/min

A 70-year-old man weighing 70 kg with a serum creatinine of 1.4 mg/dL has a Cockcroft-Gault creatinine clearance of about 49 mL/min. The rules to check first are those with a numbered step above that value: Fluconazole (50 mL/min). Flucytosine names a reduction that is not tied to a single CrCl cutoff, so read the full rule at any clearance.

How the Antifungals Cutoffs Compare With the Standard Bands

Many renally cleared drugs follow four broad creatinine clearance bands: above 50, 30-50, 15-30, and below 15 mL/min. Of the 1 CrCl cutoff named in this class, 1 sits on a standard band edge (50 mL/min), so the generic bands line up with the antifungals rules here. Where a drug's own cutoff and the generic band disagree, the drug's cutoff takes precedence.

Avoidance, Dialysis and Monitoring Notes

• Avoid or contraindicated: Amphotericin B (avoid nephrotoxin combos).
• Dialysis: no antifungals rule here mentions dialysis, so take dialysis dosing from each label.
• Levels and monitoring: Flucytosine (TDM).

Which Renal Estimate the Labels Use for Antifungals

Apply these thresholds to Cockcroft-Gault creatinine clearance in mL/min from the creatinine clearance calculator, because the labels were written against that estimate. eGFR in mL/min/1.73m² is a different quantity; see CrCl vs eGFR.

Where These Thresholds Come From

The 3 rules for antifungals were compiled from standard clinical pharmacology references (1 drug), FPnotebook (1 drug) and the FDA label (1 drug). Each threshold should still be confirmed against the current label before prescribing. Every value has been reviewed by a clinician, and each drug page links its label through DailyMed.

How Reduced Kidney Function Affects Antifungals

Renal impairment slows the elimination of antifungals and of any active metabolites the kidney clears. It also shifts the balance of benefit and harm, so dose-related adverse effects become more likely at the same nominal dose. The chart above gives the key caution for each agent. When one agent must be avoided below a cutoff, another in the class may be safer, so weigh the indication, the patient's trajectory, and monitoring availability. Record the estimate, the equation, the weight, and the date behind each dose, and re-estimate once a changing creatinine settles.

Calculate the Patient's CrCl First

Estimate creatinine clearance with the Cockcroft-Gault equation and the right dosing weight. Use actual body weight when it is below ideal body weight, ideal body weight up to 130% of ideal, and adjusted body weight above 130% of ideal, as in obesity. Re-estimate whenever kidney function may have changed, since acute illness and dehydration can lower clearance within days.

Related classes: Antivirals renal dosing (other anti-infectives with CrCl cutoffs and myelosuppression cautions); Other Antimicrobials renal dosing (other anti-infectives with CrCl cutoffs).