How can shelf-life (t90) be estimated from stability data collected at elevated temperatures?

• A. Use only high-temperature data and ignore Arrhenius relationships.
• B. Assume t90 equals the time to 50% degradation.
• C. Determine degradation rate constants at elevated temperatures, apply Arrhenius relationships to extrapolate to storage conditions, and compute t90 from the appropriate kinetic model.
• D. Use only moisture data to estimate t90.

Answer: (C)

Shelf-life estimation from accelerated stability data relies on linking how fast a product degrades to temperature using a kinetic model and the Arrhenius relationship. You determine degradation rate constants at several elevated temperatures, fit them to k = A exp(-Ea/RT), and use that relationship to extrapolate the rate constant to the actual storage temperature. With the rate constant at storage conditions in hand, you apply the appropriate kinetic model (often first-order degradation) to calculate the time required for 10% degradation (i.e., 90% potency remaining), which is t90 ≈ −ln(0.9)/k. This approach properly accounts for how temperature accelerates degradation and yields a realistic shelf-life estimate. Ignoring Arrhenius behavior or relying on high-temperature data alone would mispredict stability, and focusing on moisture data or on time to 50% degradation does not align with how shelf-life is defined.