Vancomycin AUC Calculator (Peak & Trough)
Calculate the vancomycin 24-hour AUC from two steady-state levels (peak and trough) with the Sawchuk-Zaske equations, plus ke, half-life, Vd, clearance and the dose that reaches an AUC of 400–600.
How it works
ke = ln(C_peak ÷ C_trough) ÷ (t_trough − t_peak) · Cmax = C_peak × e^(ke × (t_peak − t_inf)) · Cmin = C_trough × e^(−ke × (τ − t_trough)) · AUC_τ = t_inf × (Cmax + Cmin) ÷ 2 + (Cmax − Cmin) ÷ ke · AUC₂₄ = AUC_τ × 24 ÷ τ · Vd = [Dose/t_inf × (1 − e^(−ke·t_inf))] ÷ [ke × (Cmax − Cmin·e^(−ke·t_inf))] · new dose = dose × target AUC ÷ current AUC
The 2020 ASHP/IDSA/PIDS/SIDP consensus guideline replaced trough-only monitoring of vancomycin with AUC-guided dosing, targeting a 24-hour AUC of 400–600 mg·h/L (assuming an MIC of 1 mg/L) for serious MRSA infections; troughs alone overshoot and cause kidney injury. With two steady-state levels drawn in the same dosing interval, the elimination rate is the slope of the log-concentration line; the levels are then extrapolated back to the end of the infusion and forward to the end of the interval, and the AUC is the infusion phase (linear trapezoid) plus the elimination phase (logarithmic area). Because vancomycin follows linear kinetics, the AUC scales in proportion to the dose.
Worked example
Vancomycin 1,000 mg every 12 h infused over 1 h; peak 30 mg/L drawn 2 h after the start and trough 12 mg/L drawn at 11.5 h: ke = ln(30/12) ÷ 9.5 = 0.0965 h⁻¹ (half-life 7.2 h), true Cmax 33.0 and Cmin 11.4 mg/L, AUC over 12 h = 22.2 + 224.0 = 246 mg·h/L, so AUC₂₄ = 492 mg·h/L — within the 400–600 target. Vd is 42.1 L and clearance 4.06 L/h; keeping 1,000 mg every 12 h is appropriate.
Sources: Rybak MJ et al. Therapeutic monitoring of vancomycin for serious MRSA infections: revised consensus guideline. Am J Health Syst Pharm 2020;77:835–64 · Pai MP et al. Innovative approaches to optimizing the delivery of vancomycin in individual patients. Adv Drug Deliv Rev 2014;77:50–7
Frequently asked questions
What AUC target is used for vancomycin?
A 24-hour AUC of 400–600 mg·h/L (with an MIC of 1 mg/L by broth microdilution) for serious MRSA infections in adults, per the 2020 ASHP/IDSA/PIDS/SIDP consensus. Above 600 the risk of acute kidney injury rises without better efficacy.
When should the peak and trough be drawn?
At steady state (usually around the 4th dose), both in the same dosing interval: the peak 1–2 hours after the end of the infusion (after the distribution phase), and the trough within 30 minutes before the next dose. Record the actual draw times — they matter more than the planned ones.
Can I calculate AUC from a trough only?
Only with a Bayesian program that uses population priors. The two-level (Sawchuk-Zaske) method used here needs two concentrations; trough-only targets of 15–20 mg/L are no longer recommended for routine use.
How do I change the dose to hit the target?
Vancomycin kinetics are linear, so the new dose = current dose × target AUC ÷ measured AUC at the same interval. If the trough would be very low or the half-life is long, changing the interval may be better — recheck levels after any change.
Related calculators
Educational calculation for health professionals only, not medical advice or a prescription. Check every dose against the current product label, local protocols and a pharmacist, and adjust it for the individual patient.