Clinical & Hospital Pharmacy
Vancomycin AUC/MIC Dosing Calculator
One-compartment PK modelling of AUC₂₄/MIC, steady-state peak and trough, loading dose and an optimised regimen, following the ASHP/IDSA 2020 AUC-guided approach.
Educational tool — confirm with measured levels
AUC₂₄ / MIC ratio
647.7target 400–600
Supratherapeutic / Toxic (> 600 mg·h/L)
Clinical evaluation
Patient biometrics & clearance
Cockcroft-Gault clearance drives the whole model.
Used for Vd (0.7 L/kg).
IBW 73.2 kg · BMI 25.9 kg/m²
Must be at steady state.
Weight used for CrCl
Normal Weight: Ideal Body Weight (IBW) standard for Cockcroft-Gault.
Regimen parameters
The maintenance regimen being assessed.
Auto-calculated target regimen
The candidate whose AUC₂₄/MIC lands closest to 500.
Exposure forecast & PK parameters
Steady-state values for the regimen entered above.
The loading dose is 25–35 mg/kg of actual body weight, rounded to the nearest 250 mg and capped at 3000 mg — for severe sepsis or critically ill patients.
Alternative regimens reaching the 400–600 target
Other combinations for this patient's clearance.
| Regimen | AUC₂₄ | AUC/MIC | Pred. trough | Action |
|---|---|---|---|---|
| 750 mg q8h | 582.3 | 582.3 | 18.9 mcg/mL | |
| 750 mg q12h | 388.2 | 388.2 | 10.9 mcg/mL | |
| 1000 mg q12h | 517.6 | 517.6 | 14.5 mcg/mL | |
| 1250 mg q18h | 431.4 | 431.4 | 9.6 mcg/mL | |
| 1500 mg q18h | 517.6 | 517.6 | 11.7 mcg/mL |
Clearance is estimated from Cockcroft-Gault, then converted with the Matzke relation:
CrCl = ((140 − age) × weight) / (72 × SCr) × 0.85 if female
ke = 0.00083 × CrCl + 0.0044 (minimum 0.005 hr⁻¹)
Vd = 0.7 L/kg × actual body weight · CL = Vd × ke · t½ = 0.693 / ke
Steady-state concentrations come from the intermittent-infusion model:
Cmax,ss = [D / (t_inf × Vd × ke)] × (1 − e^−ke·t_inf) / (1 − e^−ke·τ)
Cmin,ss = Cmax,ss × e^−ke·(τ − t_inf)
Exposure is then the daily dose over clearance:
AUC₂₄ = total daily dose / CL · AUC₂₄/MIC = AUC₂₄ / MIC
The weight used for CrCl follows a heuristic: actual body weight if the patient is below IBW, adjusted body weight (IBW + 0.4 × excess) if above 120% of IBW, otherwise IBW. The optimiser searches doses of 500–2000 mg against intervals of 8–48 h and picks the combination whose AUC/MIC is nearest 500.
Common questions
Trough is a proxy, and a poor one. The 2020 ASHP/IDSA guideline found troughs of 15–20 mcg/mL routinely produce AUCs well above 600 mg·h/L, raising nephrotoxicity without improving outcomes. AUC₂₄/MIC of 400–600 is the exposure that actually correlates with cure in MRSA infection.
Volume of distribution scales with actual body weight, so Vd always uses TBW here. Creatinine clearance is different: in obesity, actual weight overestimates renal function, so adjusted body weight is used above 120% of IBW, and IBW in normal-weight patients. The Auto setting applies that rule and explains its choice.
Not always, but without one it takes four to five half-lives to reach steady state — well over two days in renal impairment. In severe sepsis or critical illness, 25–35 mg/kg of actual body weight (capped around 3000 mg) gets therapeutic exposure immediately.
Whenever renal function is not at steady state, or the one-compartment assumption breaks: acute kidney injury, haemodialysis, CRRT, extensive burns, severe ascites or major fluid shifts. Those patients need Bayesian dosing software fitted to measured concentrations.
Prepared by the PharmaWallah student team. Verify results with your textbook or instructor. Report an error · Editorial policy