- Choose the estimation mode: Mode A estimates AUC24 from the regimen + renal function when no level is available; Mode B interprets a measured steady-state trough.
- Mode A: set the weight and creatinine units, then enter age, sex, actual body weight, and the steady-state serum creatinine. Enter the regimen as a total daily dose, or as a single dose with an interval.
- Enter the organism MIC if known (broth microdilution); leave blank to assume MIC = 1 mg/L, as recommended for empiric AUC targeting.
- Mode B: enter the measured trough (drawn within 30 min before the next dose at steady state) for legacy band interpretation.
- The result shows AUC24, AUC24/MIC, the estimated CrCl and vancomycin clearance, and the trough verdict, plus a recommended action.
All computation runs in your browser; no values are stored or transmitted. Mode A is a first-order population estimate, not a Bayesian or two-level kinetic calculation.
When to Use
Use this tool when initiating or adjusting IV vancomycin for serious MRSA infection (bacteremia, endocarditis, osteomyelitis, pneumonia, or complicated skin/soft-tissue infection). The 2020 ASHP/IDSA/PIDS/SIDP consensus guideline recommends an AUC24/MIC ratio of 400–600 (assuming MIC = 1 mg/L by broth microdilution) as the pharmacodynamic target, and recommends AUC-guided monitoring in preference to trough-only monitoring.
Appropriate population
Adults with stable, steady-state renal function being treated for serious MRSA infection where vancomycin is the chosen agent. Mode A supports a starting-regimen sanity check before levels return; Mode B helps interpret a legacy trough while transitioning to AUC-guided care.
When NOT to rely on it
This first-order estimate is not a substitute for true two-level pharmacokinetics or Bayesian software, which are the guideline-preferred ways to compute AUC. Do not use during acute kidney injury, unstable creatinine, dialysis, pregnancy, or in children without specialist input — the population clearance approximation (CLvanco ≈ 0.75 × CrCl) and Cockcroft-Gault both assume steady state. Confirm the actual organism MIC and always involve clinical pharmacy.
Pearls & Pitfalls
AUC, not trough, is the target
The 2020 consensus moved away from trough-only monitoring (the old 15–20 mg/L target) because AUC-guided dosing achieves efficacy at lower overall exposure and is associated with less acute kidney injury. Aim for AUC24/MIC 400–600; an AUC above 600 adds toxicity without added benefit.
Assumptions baked into Mode A
Mode A uses CrCl by Cockcroft-Gault with actual body weight, then approximates vancomycin clearance as CLvanco ≈ 0.75 × CrCl — a widely used population estimate. At steady state, AUC24 (mg·h/L) = total daily dose (mg) ÷ CL (L/h). MIC defaults to 1 mg/L when left blank, per the guideline's empiric assumption.
Pitfalls
(1) A measured trough >15–20 mg/L, and especially an AUC24 >600, signals elevated nephrotoxicity risk — reduce the dose. (2) Troughs <10 mg/L risk subtherapeutic exposure and resistance and should not be used as an efficacy floor in AUC-based dosing. (3) The population CL factor and Cockcroft-Gault are estimates — obtain real levels and use Bayesian/two-level kinetics for definitive dosing. (4) Not validated for dialysis, AKI, paediatrics, or pregnancy.
Why Use It
Trough-only vancomycin dosing systematically overshoots exposure: to keep a trough at 15–20 mg/L, many patients accrue an AUC well above the efficacy threshold, and the resulting high exposure is the main driver of vancomycin-associated acute kidney injury. AUC-guided dosing targets the pharmacodynamic parameter that actually predicts efficacy against MRSA (AUC24/MIC ≥ 400) while capping exposure at 600 to limit toxicity. A quick first-order AUC estimate at the point of prescribing helps you pick a sensible starting regimen and recognise when a measured trough or AUC is heading into the nephrotoxic range — before waiting on Bayesian software output.
Vancomycin AUC24/MIC Estimator & Trough Interpreter
Estimate AUC24/MIC from the regimen and renal function (Mode A), or interpret a measured steady-state trough (Mode B). Target AUC24/MIC is 400–600; an AUC above 600 carries elevated nephrotoxicity risk.
⚕ Mode A: CrCl = [(140 − age) × wt(kg) × (0.85 if female)] / (72 × SCr mg/dL); CLvanco(mL/min) ≈ 0.75 × CrCl; AUC24(mg·h/L) = total daily dose(mg) ÷ CL(L/h). Target AUC24/MIC 400–600 (MIC assumed 1 mg/L if blank); >600 = elevated nephrotoxicity risk. CL ≈ 0.75 × CrCl is a population approximation — a first-order estimate, not a substitute for Bayesian/two-level kinetics or therapeutic drug monitoring. Source: Rybak MJ et al. Am J Health-Syst Pharm. 2020;77(11):835–864.
Next Steps
Use the estimate to support — not replace — therapeutic drug monitoring and pharmacy review.
- Confirm the estimated AUC with measured levels: obtain a true steady-state AUC by Bayesian software (one level acceptable) or two-level first-order kinetics, which the guideline prefers.
- If AUC24/MIC is below 400, increase the daily dose or shorten the interval; if above 600, reduce exposure to limit nephrotoxicity.
- Obtain the actual organism MIC by broth microdilution; if the MIC is >1–2 mg/L, the target AUC may be unattainable safely — consider an alternative agent.
- Monitor renal function at least every 24–48 h (more often if unstable or on concomitant nephrotoxins), and re-estimate when creatinine changes.
- Involve clinical pharmacy and, for treatment failure, persistent bacteraemia, or evolving AKI, infectious diseases / nephrology.
Evidence & References
Formula & Equations
| Quantity | Equation |
|---|---|
| Creatinine clearance (mL/min) | [(140 − age) × actual weight in kg × (0.85 if female)] ÷ (72 × SCr in mg/dL) |
| Vancomycin clearance (mL/min) | CLvanco ≈ 0.75 × CrCl (population approximation) |
| Convert clearance to L/h | CL (L/h) = CLvanco (mL/min) × 60 ÷ 1000 |
| Steady-state AUC24 (mg·h/L) | total daily dose (mg) ÷ CL (L/h) |
| AUC24/MIC ratio | AUC24 ÷ MIC (MIC assumed 1 mg/L if not entered) |
| SI / unit conversions | SCr (mg/dL) = SCr (µmol/L) ÷ 88.4; weight (kg) = lb ÷ 2.2046 |
Sanity check: 2000 mg/day with CL = 4 L/h → AUC24 = 500 mg·h/L (within the 400–600 target).
AUC₂₄/MIC bands
| AUC24/MIC | Interpretation |
|---|---|
| < 400 | Subtherapeutic — risk of treatment failure and resistance; increase dose / shorten interval |
| 400–600 | Target range for serious MRSA infection |
| > 600 | Elevated nephrotoxicity risk with no added efficacy — reduce exposure |
Legacy trough bands (Mode B)
| Trough (mg/L) | Interpretation |
|---|---|
| < 10 | Subtherapeutic — risk of resistance; avoid as an efficacy floor |
| 10–15 | Lower therapeutic range |
| 15–20 | Historical target for serious MRSA — but higher nephrotoxicity risk |
| > 20 | Toxic range — elevated AKI risk; reduce dose |
Trough bands are legacy; the 2020 consensus recommends AUC-guided monitoring (target AUC24/MIC 400–600) over trough-only targeting, which reduces vancomycin-associated acute kidney injury.
Evidence & References
The 2020 ASHP/IDSA/PIDS/SIDP revised consensus guideline recommends AUC-guided vancomycin monitoring for serious MRSA infection, with a target AUC24/MIC of 400–600 (assuming a broth-microdilution MIC of 1 mg/L), and notes that AUC-guided dosing is associated with less acute kidney injury than trough-based monitoring. The Cockcroft-Gault equation underpins the renal-function estimate; population vancomycin clearance is commonly approximated as roughly three-quarters of creatinine clearance.
- Rybak MJ, Le J, Lodise TP, et al. Therapeutic monitoring of vancomycin for serious methicillin-resistant Staphylococcus aureus infections: A revised consensus guideline and review by the American Society of Health-System Pharmacists, the Infectious Diseases Society of America, the Pediatric Infectious Diseases Society, and the Society of Infectious Diseases Pharmacists. Am J Health-Syst Pharm. 2020;77(11):835–864.
- Cockcroft DW, Gault MH. Prediction of Creatinine Clearance from Serum Creatinine. Nephron. 1976;16(1):31–41.
- Kidney Disease: Improving Global Outcomes (KDIGO) CKD Work Group. KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease. Kidney Int. 2024;105(4S):S117–S314.
