Drug Half-Life Calculator: Medication Elimination
Calculate how long a substance remains in the body.
What is Biological Half-Life?
The half-life of a drug is the time it takes for the concentration of the substance in the body to be reduced by exactly one half (50%). It helps determine dosing schedules and withdrawal times.
The Formula
- The decay is exponential.
- Formula: Remaining Amount = Initial Dose × (0.5)^(Time Elapsed / Half-Life).
- Generally, it takes about 5.5 half-lives for a drug to be considered effectively eliminated from the system.
Pharmacology FAQs
Does half-life change with dose?
For most drugs (first-order kinetics), the half-life remains constant regardless of the dose. For some (like alcohol), the rate of elimination is constant rather than proportional.