Drug Half-Life Calculator
Calculate drug elimination and remaining concentration over time using pharmacokinetic principles
Calculate Drug Half-Life
Choose a common drug or select "Custom Drug" to enter your own values
Time for drug concentration to reduce by half
Amount of drug administered initially
Calculate remaining drug at specific time
Medical Disclaimer
This calculator is for educational purposes only and should not replace professional medical advice. Drug elimination can vary significantly between individuals due to factors like age, kidney function, liver function, and drug interactions. Always consult healthcare professionals for medical decisions.
Elimination Analysis
Example Calculation
Adderall Half-Life Example
Scenario: Patient took 20 mg of Adderall 6 hours ago
Adderall half-life: ~12 hours
Time elapsed: 6 hours (0.5 half-lives)
Calculation: 20 mg × 0.5^(6/12) = 20 mg × 0.5^0.5
Result
Remaining drug: 20 mg × 0.707 = 14.14 mg
Percentage remaining: 70.7% of original dose
Interpretation: Significant drug concentration still present
Drug Half-Life Ranges
Short (Minutes)
Epinephrine: 2-3 min
Rapid elimination
Medium (Hours)
Morphine: 1-7 hrs
Moderate elimination
Long (Days)
Amiodarone: 26-107 days
Slow elimination
Key Principles
After 5 half-lives, ~97% of drug is eliminated
Half-life varies between individuals
Affected by age, kidney, and liver function
Drug interactions can alter elimination
Used to determine dosing intervals
Understanding Drug Half-Life
What is Drug Half-Life?
Drug half-life is the time it takes for the concentration of a drug in blood plasma to reduce by exactly half. This pharmacokinetic parameter helps determine how long a drug remains active in the body and guides dosing schedules.
Clinical Significance
- •Determines dosing frequency
- •Predicts time to steady state
- •Assesses drug accumulation risk
- •Guides withdrawal timing
Calculation Formula
Dosage(t) = Dosage(0) × 0.5^(t/T)
- Dosage(t): Drug amount at time t
- Dosage(0): Initial drug amount
- t: Time elapsed since administration
- T: Drug half-life
Note: Individual factors like age, genetics, organ function, and drug interactions can significantly alter elimination rates.