How is creatinine clearance estimated?

The tool uses the Cockcroft-Gault equation: CrCl = ((140 − age) × weight) ÷ (72 × serum creatinine in mg/dL), multiplied by 0.85 for females. If creatinine is entered in µmol/L it is divided by 88.4 to convert to mg/dL first.

What is the vancomycin AUC target?

The 2020 ASHP/IDSA guideline recommends AUC-guided dosing targeting an AUC/MIC ratio of 400–600 mg·h/L, assuming an MIC of 1 mg/L by broth microdilution. Trough-only monitoring is no longer the preferred approach for serious MRSA infections.

How are loading and maintenance doses chosen?

A loading dose of about 25 mg/kg (range 20–35) is used for serious infections, and maintenance is 15–20 mg/kg per dose. The interval is selected from renal function, lengthening as creatinine clearance falls.

How is the dosing interval picked?

As a rough guide: CrCl above 90 mL/min suggests every 8–12 hours, 50–90 every 12 hours, 20–49 every 24 hours, and below 20 every 24–48 hours dosed by levels. Confirm with measured pharmacokinetics.

Should I rely on this estimate alone?

No. This is a starting estimate only. Confirm and adjust dosing with two-level pharmacokinetic sampling or Bayesian software to hit the measured AUC, round doses to the nearest 250 mg, and cap single doses around 2–3 g.

What is the Vancomycin Dosing & AUC/MIC Calculator?

Free vancomycin dosing calculator. Enter age, weight, sex, and serum creatinine to estimate Cockcroft-Gault creatinine clearance, a loading dose, a maintenance dose range, and a starting interval targeting AUC/MIC 400–600 per ASHP 2020. Runs in your browser. It runs free in your browser on Gera Tools, with nothing uploaded.

Vancomycin Dosing & AUC/MIC Calculator

Name: Vancomycin Dosing & AUC/MIC Calculator
Creator: Gera Tools
License: https://creativecommons.org/licenses/by/4.0/

This calculator gives a starting vancomycin regimen based on the patient’s renal function, following the 2020 ASHP/IDSA move from trough-only monitoring to AUC-guided dosing for serious MRSA infections. It is built for infectious-disease pharmacists and physicians initiating therapy.

How it works

First it estimates renal function with the Cockcroft-Gault equation:

CrCl (mL/min) = ((140 − age) × weight) ÷ (72 × SCr) × (0.85 if female)

with serum creatinine (SCr) in mg/dL. If you enter creatinine in µmol/L it is divided by 88.4 to convert first. From the clearance it proposes:

Loading dose — about 25 mg/kg (guideline range 20–35) for serious infections, to reach therapeutic exposure quickly.
Maintenance dose — 15–20 mg/kg per dose.
Interval — chosen from renal function: faster clearance means more frequent dosing, slower clearance means longer intervals.

The AUC/MIC target

The guideline target is an AUC/MIC of 400–600 mg·h/L, conventionally assuming an MIC of 1 mg/L by broth microdilution. AUC-guided dosing reduces nephrotoxicity compared with chasing high troughs while maintaining efficacy.

Notes and safety

This tool produces a starting estimate only. Confirm and refine the regimen with two-level pharmacokinetic sampling or Bayesian dosing software to hit the measured AUC, especially in unstable renal function, obesity, or critical illness. In practice, round doses to the nearest 250 mg and cap single doses around 2–3 g. Monitor renal function throughout therapy. All calculation runs locally in your browser.

Why the shift to AUC-guided dosing matters

For two decades, most clinicians targeted a vancomycin trough concentration of 15–20 mg/L and treated that as a proxy for efficacy. The 2020 ASHP/IDSA/SIDP guideline update moved away from trough-only monitoring because the evidence showed it does not reliably predict the AUC, and chasing high troughs drove nephrotoxicity without guaranteeing therapeutic exposure. AUC-guided dosing directly models how much drug the pathogen is exposed to over time, which is the pharmacodynamic driver of outcome for MRSA infections.

Interpreting the Cockcroft-Gault estimate

The Cockcroft-Gault equation was developed and validated in populations that differ from some modern patient groups. In patients with very low serum creatinine (for example, older patients with muscle wasting), the equation overestimates clearance and a minimum creatinine of 0.6–0.7 mg/dL is sometimes applied. In morbid obesity, using total body weight inflates the estimate; many centres use adjusted or ideal body weight for the weight term. In critical illness, rapidly changing creatinine means the steady-state assumption breaks down and the estimate lags behind real function. This tool calculates the standard equation as entered; clinical adjustment for these scenarios requires pharmacist or physician judgment.

Practical workflow

The output here is a starting regimen. In practice, after the first two doses pharmacokineticists draw a trough (or ideally a trough and mid-interval concentration) to calculate a measured AUC using Bayesian software. If the measured AUC falls outside 400–600 mg·h/L the dose, interval, or both are adjusted. Patients on therapy for more than a few days, or whose renal function changes, need the cycle repeated. A single set of levels is not enough to confirm ongoing therapeutic adequacy.