Vancomycin Calculator

Visual Dosing & PK Modeling

by
RxToDose

Dose and Level Inputs

Enter doses and levels below. You can copy and paste a selection from Excel or another spreadsheet program directly into the grid.

Levels

Low
High

Calculated drug concentration (mg/L) per hour.

How to Use This Calculator

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RxToDose is a client-side simulation engine designed to help clinicians visualize and optimize Vancomycin dosing. Follow the guide below to understand the demographic models, dynamic level-anchoring, and simulation algorithms.

1.

Patient Demographics & Initial Estimation

Input patient demographics (Age, Gender, Weight, Height, SCr) to initialize population-based pharmacokinetic estimates:

  • Model Selection: The calculator dynamically assigns a population model (e.g., Buelga for general patients, Adane for BMI ≥ 40 and Weight ≥ 120kg).
  • ICU Checkbox: Checking this shifts the estimation model to Roberts (ICU, non-obese) or Masich (ICU, BMI ≥ 30) to account for altered ICU kinetics.
  • Body Weight Adjustments: Clinically validated formulas calculate Ideal Body Weight (IBW) and Adjusted Body Weight (ABW) automatically for clearance estimates.
Pediatric Warning: This calculator is strictly calibrated for adult protocols (≥ 18 years). Use for pediatric populations with extreme caution.
2.

Entering Regimens & Measured Levels

The 24-hour grid allows you to input doses, levels, and hemodialysis cycles across multiple days:

  • Doses: Enter raw values ≥ 100 (e.g., 1250) or values with units (e.g., 1g, 1.5gm). Doses are simulated as zero-order infusions.
  • Measured Levels: Enter values < 100 (e.g., 15.2) at the specific hour they were drawn to dynamically calibrate kinetics.
  • Hemodialysis Sessions: Type HD in the grid at the dialysis hours to apply an additional dialysis-specific clearance rate (default: 12%/hr).
Smart Paste: Quickly copy and paste patient strings (e.g. 34/M, 80kg, 168cm, 0.8) directly into the demographics parser or paste grids from Excel.
3.

Dynamic Ke Solving & Infusion Modeling

The simulation engine uses patient inputs to solve and fit pharmacokinetic curves:

  • Dynamic Calibration: Entering a measured concentration prompts the calculator to scan backward, locate the last dose, and solve for the patient-specific elimination rate constant (Ke) that matches the level.
  • Zero-Order Infusion Logic: Instead of instantaneous bolus modeling, the calculator simulates zero-order infusions to match standard administration times:
    • Doses ≤ 1,000 mg: 1-hour infusion
    • Doses 1,001–1,250 mg: 1.5-hour infusion
    • Doses ≥ 1,250 mg: 2-hour infusion
Hourly Resolution: The calculator operates on a strict hourly grid. Doses and level draws should be rounded to the nearest hour.
4.

Interpreting Outputs & Dosing Suggestions

Observe the concentration curves and utilize the regimen optimization panel:

  • Concentration Chart: Plots hourly levels. The green-shaded band shows the traditional target therapeutic trough window (10–15 mg/L).
  • Regimen Suggester: Enter your target trough (e.g., 15-20) and click Suggest Regimen. The tool computes expected troughs and estimated AUC/24hr values for several intervals.
  • Static Regimens: Compares standard regimens side-by-side using the patient's individual clearance.
Clinical Pearl: Modern consensus guidelines emphasize targeting an AUC/MIC ratio of 400–600 (assuming an MIC of 1 mg/L). Check the AUC/24h estimates in the parameter panel.

Pharmacokinetic Estimation Models

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The calculator dynamically selects a pharmacokinetic model based on the patient's condition (ICU vs. Non-ICU) and Body Mass Index (BMI). You can override this selection manually. Below are the equations utilized in each model.

Core Weight & Clearance Formulations

  • Ideal Body Weight (Devine):
    Male = 50 + 2.3 × (Height_in - 60)
    Female = 45.5 + 2.3 × (Height_in - 60)
  • Adjusted Body Weight:
    ABW = IBW + 0.4 × (TotalBW - IBW)
  • CrCl (Cockcroft-Gault):
    CrCl = ((140 - Age) × Weight_kg) / (72 × SCr) × (0.85 if Female)
  • Ke (Elimination Rate Constant):
    Ke = Clearance / Vd
Cockcroft DW, Gault MH. (1976). Prediction of creatinine clearance from serum creatinine. Nephron, 16(1), 31-41.

Matzke/Rushing-Ambrose (Legacy)

Traditional estimation parameters. Kept for reference.

  • Vd: 0.17 × Age + 0.22 × TotalBW(kg) + 15
  • CL: ((0.689 × CrCl) + 3.66) × 0.06
Matzke GR, et al. (1986). Pharmacokinetics of vancomycin in patients with various degrees of renal function. Antimicrob Agents Chemother, 30(3), 433-437.

Buelga (General Hospitalized)

Designed for general hospitalized, non-obese populations.

  • Vd: 0.98 × TotalBW(kg)
  • CL: 1.08 × (Jaffe-Adj CrCl in L/hr)
  • * Uses Jaffe-adjusted SCr: (SCr × 1.065) + 0.067
Buelga DS, et al. (2005). Population pharmacokinetic analysis of vancomycin in patients with hematological malignancies. Antimicrob Agents Chemother, 49(12), 4934-4941.

Adane (Extreme Obesity)

Targeted for patients with BMI ≥ 40 and Weight ≥ 120kg.

  • Vd: 0.51 × TotalBW(kg)
  • CL: 6.54 × (Normalized_CrCl / 125)
  • * Normalized_CrCl = CrCl × (1.73 / BSA)
Adane ED, et al. (2015). Pharmacokinetics of vancomycin in extremely obese patients with suspected or confirmed Staphylococcus aureus infections. Pharmacotherapy, 35(2), 127-139.

Roberts (Critically Ill)

Designed for critically ill (ICU) patients without extreme obesity.

  • Vd: 1.53 × TotalBW(kg)
  • CL: 4.58 × (Normalized_CrCl / 100)
  • * Normalized_CrCl = CrCl × (1.73 / BSA)
Roberts JA, et al. (2011). Vancomycin dosing in critically ill patients: Robust methods for improved continuous-infusion regimens. Antimicrob Agents Chemother, 55(6), 2704-2709.

Masich (Critically Ill & Obese)

Specifically modeled for ICU patients with BMI ≥ 30.

  • Vd: 0.78 × TotalBW(kg)
  • CL: 3.23 × (CrCl / 40)^0.69
Masich AM, et al. (2020). Vancomycin pharmacokinetics in obese patients with sepsis or septic shock. Pharmacotherapy, 40(3), 211-220.

Frequently Asked Questions

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Glossary & Definitions

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Pharmacokinetics

Ke (Elimination Rate Constant)
The fraction of drug removed from the body per unit of time (hr⁻¹).
Vd (Volume of Distribution)
Theoretical volume necessary to contain the total drug amount at the same concentration observed in blood plasma.
Cl (Clearance)
Volume of plasma completely cleared of drug per unit time. Calculated as Ke × Vd.
CrCl (Creatinine Clearance)
Estimate of renal function (GFR) via Cockcroft-Gault. Used to estimate initial vancomycin clearance.
Weight Metrics

BMI: Body Mass Index.

IBW: Ideal Body Weight (Devine formula).

ABW: Adjusted Body Weight (for obesity dosing).

Calculator Settings

Level Recognition Cutoff
Numbers below this value are treated as levels (mg/L).
Numbers above are treated as doses (mg).
Default: 100
HD Identifier
The text code used to mark a cell as a Hemodialysis session. Default is "HD".
HD% / hr
Percentage of drug removed per hour during dialysis. Default is 12% (approx. 40-50% for 4 hours).
Ke Convergence Minimum
Precision threshold for the iterative calculation loop. Smaller numbers = higher precision.
Number of Doses to Apply
Determines how many future doses are projected onto the grid when clicking "Apply".

References & Guidelines

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Clinical Parameters & Pharmacokinetic Formulas

Comprehensive breakdown of demographic calculations and population estimates

Demographics Required

Please input patient demographics (Age, Gender, Weight, Height, SCr) to calculate estimated parameters first.