What is the target vancomycin AUC/MIC ratio?

The 2020 ASHP/IDSA/PIDS guidelines recommend a target AUC/MIC of 400–600 mg·h/L for serious MRSA infections, assuming a vancomycin MIC ≤1 mcg/mL. This replaces the previous trough-only target of 15–20 mcg/mL.

How is vancomycin AUC calculated from two levels?

Two serum vancomycin levels (a peak drawn 1–2 hours after infusion and a trough drawn before the next dose) are used to estimate the elimination rate constant (Ke). Using first-order kinetics, the AUC₂₄ is calculated by integrating the concentration-time curve over 24 hours. This two-level approach is recommended over trough-only monitoring by current guidelines.

Can I use a single trough level to estimate vancomycin AUC?

A single trough can provide a rough AUC estimate, but this is less accurate than two-level monitoring. Trough values of 15–20 mcg/mL roughly correspond to AUC 400–600 for many patients, but the relationship varies with elimination half-life and dosing interval. Two-level or Bayesian methods are preferred.

What is the risk of vancomycin AUC greater than 600?

AUC values above 600 mg·h/L are associated with increased risk of nephrotoxicity, particularly when sustained over multiple days or combined with other nephrotoxic agents (e.g., piperacillin-tazobactam, aminoglycosides, NSAIDs, IV contrast). AUC above 700–800 significantly increases nephrotoxicity risk.

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Vancomycin AUC₂₄/MIC Calculator

Estimate vancomycin AUC₂₄ and AUC/MIC ratio using two-level pharmacokinetic estimation or trough-based approximation. Based on the 2020 ASHP/IDSA/PIDS consensus guidelines.

Calculation Mode

Patient Information

Sex

Age (years)

Weight (kg)

Serum creatinine (mg/dL)

Vancomycin Levels

Peak level (mcg/mL) Drawn 1–2 h after infusion end

Time of peak after dose (h) Hours from start of infusion

Trough level (mcg/mL) Drawn just before next dose

Time of trough after dose (h) Hours from start of infusion

Dosing interval

Infusion duration (h)

Assumed MIC (mcg/mL) Broth microdilution MIC; target AUC/MIC applies to MIC ≤1

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Enter inputs above to calculate AUC₂₄.

Disclaimer: This is a simplified first-order pharmacokinetic estimation. Bayesian software (e.g., PrecisePK, DoseMeRx) is preferred for clinical AUC monitoring. Not a substitute for clinical judgment or pharmacy consultation.

Clinical Pearls

Target AUC/MIC 400–600 mg·h/L for serious MRSA infections (bacteremia, endocarditis, osteomyelitis, pneumonia) when MIC ≤1 mcg/mL.
Two-level monitoring (peak + trough) is recommended over trough-only by 2020 ASHP/IDSA/PIDS guidelines.
Bayesian estimation using clinical software is the gold standard. This calculator provides a simplified first-order kinetic estimate.
Nephrotoxicity risk increases significantly with AUC >600, especially with concomitant nephrotoxins (piperacillin-tazobactam, aminoglycosides, NSAIDs, IV contrast).
Monitor SCr at least every 48–72 hours during vancomycin therapy. More frequently for ICU patients or those with unstable renal function.
For MIC = 2 mcg/mL, achieving AUC/MIC ≥400 requires potentially toxic AUC values (≥800). Consider alternative agents.

AUC/MIC Interpretation

< 400Subtherapeutic — risk of treatment failure

400–600Therapeutic target — optimal efficacy & safety

600–700Supratherapeutic — monitor closely

> 700High nephrotoxicity risk — dose reduction needed

Trough Correlation (Approximate)

For q12h dosing with typical half-life:

Trough <10AUC likely <400

Trough 10–15AUC ~350–500

Trough 15–20AUC ~400–600

Trough >20AUC likely >600

References

Rybak MJ, Le J, Lodise TP, et al. Therapeutic monitoring of vancomycin for serious methicillin-resistant Staphylococcus aureus infections: A revised consensus guideline. Am J Health-Syst Pharm. 2020;77(11):835–864.
Neely MN, et al. Are vancomycin trough concentrations adequate for optimal dosing? Antimicrob Agents Chemother. 2014;58(1):309–316.
Pai MP, Neely M, Rodvold KA, Lodise TP. Innovative approaches to optimizing the delivery of vancomycin in individual patients. Adv Drug Deliv Rev. 2014;77:50–57.

Related Tools

About This Tool

What Is Vancomycin AUC/MIC Monitoring?

Vancomycin AUC/MIC-guided dosing represents the current standard of care for therapeutic drug monitoring (TDM) of vancomycin in serious MRSA infections. The 2020 ASHP/IDSA/PIDS consensus guidelines recommend targeting an AUC₂₄/MIC ratio of 400–600 mg·h/L (assuming MIC ≤1 mcg/mL by broth microdilution) rather than the previously recommended trough-only strategy of 15–20 mcg/mL.

Why AUC/MIC Instead of Trough Levels?

Multiple studies have demonstrated that AUC/MIC is the pharmacokinetic/pharmacodynamic (PK/PD) index most predictive of vancomycin efficacy against MRSA. Trough-only monitoring can lead to unnecessarily high vancomycin exposure to achieve "therapeutic" troughs, particularly with aggressive dosing regimens. AUC-guided dosing has been associated with similar or improved clinical outcomes and significantly less nephrotoxicity compared to trough-only strategies.

Two-Level vs. Trough-Only Estimation

The two-level method uses a peak concentration (drawn 1–2 hours after infusion end) and a trough concentration (drawn within 30 minutes before the next dose) to calculate the elimination rate constant (Ke) and estimate AUC₂₄ using first-order kinetic equations. This is more accurate than trough-only estimation.

The trough-only method uses population-based pharmacokinetic estimates of Ke (derived from patient-specific CrCl) to approximate AUC from a single trough value. This is less accurate but may be used when only one level is available.

Pharmacokinetic Method (Two-Level)

This calculator uses first-order pharmacokinetics:

Ke (elimination rate constant) = ln(Peak/Trough) / Δt, where Δt is the time between peak and trough samples
t½ (half-life) = 0.693 / Ke
AUC₂₄ is calculated by linear-log trapezoidal integration over the dosing interval, then extrapolated to 24 hours

🔑 Clinical Pearls

Bayesian software (PrecisePK, DoseMeRx, InsightRx) is the preferred method for AUC estimation and can work with fewer or mistimed levels.
For MRSA isolates with MIC = 2 mcg/mL, achieving AUC/MIC ≥400 requires AUC ≥800 — consider alternative antimicrobials (daptomycin, linezolid, TMP-SMX).
Concomitant piperacillin-tazobactam increases nephrotoxicity risk independently. Monitor renal function closely and consider alternatives.
In obese patients, use actual body weight for vancomycin dosing but expect longer half-life and higher Vd.
Loading doses (25–30 mg/kg actual body weight) are recommended for serious infections to rapidly achieve therapeutic concentrations.
Reassess AUC after significant changes in renal function (SCr change ≥0.3 mg/dL or ≥50%).

Key References

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 ASHP, IDSA, PIDS, and SIDP. Am J Health-Syst Pharm. 2020;77(11):835–864.
Neely MN, Youn G, Jones B, et al. Are vancomycin trough concentrations adequate for optimal dosing? Antimicrob Agents Chemother. 2014;58(1):309–316.
Lodise TP, Drusano GL, Zasowski E, et al. Vancomycin exposure in patients with methicillin-resistant Staphylococcus aureus bloodstream infections: how much is enough? Clin Infect Dis. 2014;59(5):666–675.
Pai MP, Neely M, Rodvold KA, Lodise TP. Innovative approaches to optimizing the delivery of vancomycin in individual patients. Adv Drug Deliv Rev. 2014;77:50–57.

Formula last verified: February 2026