Vancomycin Calculator

Visual Dosing & Pharmacokinetic Modeling

Inputs

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

Levels

Shows the calculated drug concentration (mg/L) for each hour.

Concentration Graph

  1. Cockcroft, D. W., & Gault, M. H. (1976). Prediction of creatinine clearance from serum creatinine. Nephron, 16(1), 31-41.
  2. Matzke, G. R., et al. (1986). Pharmacokinetics of vancomycin in patients with various degrees of renal function. Antimicrobial agents and chemotherapy, 30(3), 433-437.
  3. Rybak, M. J., et al. (2020). Therapeutic monitoring of vancomycin for serious methicillin-resistant Staphylococcus aureus infections: A revised consensus guideline and review. American journal of health-system pharmacy, 77(11), 835-864.
  4. Bauer, L. A. (2019). Applied Clinical Pharmacokinetics (4th ed.). McGraw-Hill Education.
  5. Murphy, J. E. (2017). Clinical Pharmacokinetics (6th ed.). ASHP.
  6. Winter, M. E. (2010). Basic Clinical Pharmacokinetics (5th ed.). Lippincott Williams & Wilkins.
  7. Buelga, D. S., et al. (2005). Population pharmacokinetic analysis of vancomycin in patients with hematological malignancies. Antimicrobial agents and chemotherapy, 49(12), 4934-4941.

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How to Use This Calculator

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1. The Core Interface

The interactive grid represents the patient's pharmacokinetic profile over 24 hours.

  • Inputs: Enter doses in milligrams (e.g., 1000) or grams (e.g., 1g).
  • Levels: Enter measured serum concentrations (e.g., 12.5).
  • HD: Mark hemodialysis hours with "HD".

2. Dynamic Simulation

RxToDose acts as a simulation engine. When you enter a level, the system looks backward to find the most recent dose and calculates a patient-specific elimination rate constant (Ke). This new parameter is "locked in" and used to project future levels.

3. Interpretation & Dosing

Serum levels are plotted on the grid using a dynamic simulation that calculates the best-fit elimination rate constant (Ke) from your inputs. This allows you to use the grid as a predictive tool to forecast drug concentrations at specific times.

The Concentration Graph visualizes the data from the grid. The green shaded area represents the traditional therapeutic trough range (10-15 mg/L). Use the Dose Recommendations panel to generate a regimen based on your target trough.

Limitation: Hourly Resolution

Please note that this tool operates on a strict hourly resolution. All inputs and outputs correspond to the exact hour (e.g., 14:00). The calculator does not account for half-hour intervals (e.g., 14:30) or specific minute-based variances in administration or lab draw times.

Clinical Pearl: AUC vs. Trough

While this tool visualizes trough levels, modern vancomycin monitoring often targets an AUC/MIC ratio of 400-600. The "Calculated Patient Parameters" panel provides an estimated AUC/24hr based on the current dosing regimen and calculated clearance.

Frequently Asked Questions

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Why choose this over other calculators?

RxToDose is designed for speed and flexibility. Its primary advantage is the ease of input—you can directly paste data from Excel to visualize dosing schedules, levels, and predicted levels. It acts as an instant vancomycin level interpreter, providing dynamic graphs and calculating the elimination rate constant (Ke) at each individual point.

Is this calculator HIPAA compliant?

Yes. Unlike other calculators that process data on a server, RxToDose runs entirely in your browser using JavaScript. No patient data (Age, Weight, Creatinine, or Doses) ever leaves your device. It is inherently HIPAA-compliant because no Protected Health Information (PHI) is ever transmitted over the internet or stored in a database.

Does this calculator dose off of AUC targets or troughs?

While this calculator provides robust AUC calculations to support clinical decision-making, the specific dosing recommendations provided in the "Recommendations" panel are still based on traditional trough targets.

How does the calculator handle obesity?

For patients with a BMI > 30 or morbid obesity, the tool automatically calculates Ideal Body Weight (IBW) and Adjusted Body Weight (ABW) to ensure accurate dosing without overdosing adipose tissue.

Is there a cost to use this tool?

No, RxToDose is a completely free PK calculator. It was built to serve as a reliable addition to any clinical pharmacist toolkit and is accessible offline, making it ideal for pharmacy students, pharmacy residents, and practicing clinical pharmacists where quick, secure, and reliable answers are needed on the go.

Are there any other tools available?

The vancomycin calculator was the first tool launched, but RxToDose is expanding. Currently, tools for TPN calculations, statin equivalence, and weight calculations (BMI, IBW, ABW) are available. More tools are in development, including calculators for aminoglycosides such as gentamicin, tobramycin, and amikacin.

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".