Drug Half Life Calculator

Calculate how long it takes for a drug’s concentration to reduce by half and estimate remaining drug levels over time.

Understanding Drug Half-Life

Drug half-life is the time required for the concentration of a drug in the body to decrease by 50%. This concept is crucial for:

• Determining dosing intervals
• Estimating drug clearance time
• Understanding drug accumulation
• Planning medication schedules

How Half-Life Works

1. First Half-Life

   • Initial concentration reduces by 50%
   • Example: 100mg → 50mg

2. Second Half-Life

   • Remaining amount reduces by another 50%
   • Example: 50mg → 25mg

3. Subsequent Half-Lives

   • Pattern continues
   • After 4 half-lives: ~6.25% remains
   • After 5 half-lives: ~3.125% remains

How to Use This Calculator

1. Enter the initial drug concentration
2. Input the drug’s known half-life
3. Specify the time period
4. The calculator will show:
   • Remaining drug concentration
   • Percentage remaining
   • Number of half-lives elapsed
   • Time until specific threshold reached

Common Half-Life Examples

• Caffeine: 5 hours
• Ibuprofen: 2 hours
• Acetaminophen: 2-3 hours
• Fluoxetine: 4-6 days
• Diazepam: 20-50 hours
• Amoxicillin: 1-1.5 hours

Factors Affecting Half-Life

• Age
• Liver function
• Kidney function
• Body weight
• Metabolism
• Drug interactions
• Hydration status
• Medical conditions

Important Notes

Medical Disclaimer

This calculator is for educational and research purposes only. Do not use it to make medical decisions. Always:

• Follow prescribed dosing schedules
• Consult healthcare providers about medications
• Never adjust medication timing without medical advice
• Consider individual variations in drug metabolism

Limitations

• Calculations assume ideal conditions
• Individual metabolism varies
• Multiple factors affect actual drug clearance
• Some drugs have complex elimination patterns

Professional Use

For healthcare professionals:

• Use as a reference tool
• Consider patient-specific factors
• Account for drug-drug interactions
• Monitor patient response
• Document actual clearance patterns

Remember: This calculator provides theoretical estimates. Always rely on clinical guidelines and professional judgment for patient care.