New Dose and Interval From Two Levels (Sawchuk-Zaske)
Half-life, volume of distribution and extrapolated peak and trough from two levels after an intermittent infusion.
Open the calculator → Runs in your browser. Data leaves only if you deliberately send a problem report from the interactive tool.
Example
- Levels follow a first dose (first) or a dose at steady state
- At steady state
- Dose given
- 120 mg
- Infusion time
- 1 hours
- Dosing interval
- 8 hours
- First level
- 6 mg/L
- First level: hours after the infusion ended
- 0.5 hours
- Second level
- 1.5 mg/L
- Second level: hours after the infusion ended
- 6 hours
Result: Half-life 2.75 hours and volume of distribution 17.98 L, from a peak of 6.806 mg/L and a trough of 1.166 mg/L.
The tool opens with these values already filled in. Replace them with your own.
What you enter
- Levels follow a first dose (first) or a dose at steady state (steady)
- Dose given
- Infusion time
- Dosing interval
- First level
- First level: hours after the infusion ended
- Second level
- Second level: hours after the infusion ended
The other 4 fields
- Pre-dose level (first dose only; optional)
- Weight, for L/kg (optional)
- Desired peak (optional, with a trough)
- Desired trough (optional)
How this is calculated
Citation
Sawchuk RJ, Zaske DE, Cipolle RJ, Wargin WA, Strate RG. Kinetic model for gentamicin dosing with the use of individual patient parameters. Clin Pharmacol Ther. 1977;21(3):362-369. The equations are the closed-form solution of its one-compartment model. Read the source ↗
A reference and educational tool. Not medical, legal, or financial advice, and not a substitute for clinician judgment.