Merck Stability & Shelf Life Calculator
Standard refrigerated (5°C) or room temp (25°C).
The actual temperature during the deviation.
Total time spent at the excursion temperature.
Standard default for pharma is 83.14 (20 kcal/mol).
Analysis Results
Acceleration Factor (AF):
Equivalent Storage Time: hours
Shelf Life Loss: days
Understanding the Merck Stability Calculator
In pharmaceutical manufacturing and distribution, products are often exposed to temperatures outside their labeled storage conditions. This is known as a temperature excursion. The Merck Stability Calculator uses the Arrhenius Equation to determine how much "shelf life" is consumed during these brief periods of heat stress.
How the Calculation Works
Stability calculations rely on the principle that chemical degradation rates increase as temperature rises. The primary formula used is:
k = A * e^(-Ea / RT)
Where:
- k: Rate constant of degradation.
- Ea: Activation Energy (typically 70-100 kJ/mol for pharmaceuticals).
- R: Gas Constant (8.314 J/mol·K).
- T: Absolute temperature in Kelvin.
Practical Example
Imagine a biologic drug meant to be stored at 5°C. During shipping, a sensor shows it was exposed to 25°C for 24 hours. Using an Activation Energy of 83.14 kJ/mol:
- The Acceleration Factor would be approximately 10.5.
- This means 1 hour at 25°C is equivalent to 10.5 hours at 5°C.
- The 24-hour excursion effectively "used up" 252 hours (10.5 days) of the product's refrigerated shelf life.
Key Terms for Stability Testing
| Term | Definition |
|---|---|
| Mean Kinetic Temperature (MKT) | A single derived temperature that simulates the non-linear effect of temperature variations over time. |
| Activation Energy (Ea) | The energy barrier that must be overcome for a chemical reaction (degradation) to occur. |
| Q10 Factor | The factor by which the rate of degradation increases for every 10-degree rise in temperature. |