Half-Life Washout Calculator
Calculate the time required for a medication to be effectively cleared from your system (below 5% of steady-state levels).
Medical Disclaimer
This calculator is for informational and educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before making decisions about your health. Never disregard professional medical advice or delay seeking it because of results from this tool.
Inputs
Results
Washout Time
51.9 hours
Washout Time
2.2 days
How to Use This Calculator
- Enter the medication's Half-Life in hours — find this on the prescribing information, FDA label, or a pharmacology reference.
- Enter the number of Doses Per Day (affects steady-state accumulation level).
- Enter the Days at Steady State — how many days you have been taking the medication consistently.
- Review the Washout Time in hours and days — this represents the time for the drug to fall below 5% of steady-state levels (approximately 4–5 half-lives).
- Note the Percent Remaining at 24h and 48h to plan procedure timing, drug switches, or pregnancy considerations.
How the result changes with Half-Life
| Half-Life | Washout Time | Washout Time |
|---|---|---|
| 50 | 216.1 hours | 9 days |
| 175 | 756.3 hours | 31.5 days |
| 325 | 1,404.6 hours | 58.5 days |
| 450 | 1,944.9 hours | 81 days |
What each input means
- Half-Life
- Elimination half-life of the medication in hours.
- Doses Per Day
- Number of doses taken per day (affects steady-state accumulation).
- Days at Steady State
- Number of days you have been taking the medication consistently.
How this is calculated
Worked example, using the default values
- Identify Input ParametersHalf-Life = 12, Doses Per Day = 1, Days at Steady State = 7 = 3 input(s) provided
- Calculate Washout TimeWashout Time51.9 = 51.9
- Calculate Washout TimeWashout Time2.2 = 2.2
- Calculate Half-Lives to ClearHalf-Lives to Clear4.32 = 4.32
- Calculate Time to Steady StateTime to Steady State2.5 = 2.5
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