Drug Half-Life Calculator
Track remaining drug dose across half-life cycles with common medication presets and elimination table.
Drug Half-Life in Pharmacology
Drug half-life is the time required for plasma concentration to fall by half. It guides dosing intervals and predicts remaining drug amount over time. For general decay math, see the Half-Life Calculator; for weight-based dosing, use the Dosage Calculator.
Elimination Formula
Remaining dose at time t equals initial dose multiplied by 0.5 raised to the power of t divided by half-life. After one half-life, 50% remains; after two, 25%; after three, 12.5%.
Common Medication Presets
The calculator includes presets such as acetaminophen, morphine, warfarin, and epinephrine with typical half-life ranges. Custom values support any drug when you know its elimination half-life.
Frequently Asked Questions
What is the drug half-life equation?
D(t) = D₀ × 0.5^(t/T), where T is half-life and t is elapsed time.
Why does half-life matter clinically?
It helps determine dosing frequency and how long a drug stays active in the body.
Which drug has a very short half-life?
Epinephrine has one of the shortest half-lives, often around 2 to 3 minutes.
How much drug remains after one half-life?
Exactly 50% of the initial dose remains after one complete half-life period.
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