Capen, Robert, et al. “On the Shelf Life of Pharmaceutical Products.” AAPS PharmSciTech, vol. 13, no. 3, Sept. 2012, pp. 911–18. PubMed, doi:10.1208/s12249-012-9815-2.
This article discusses the current methodology and definitions used when talking about batches of pharmaceutical products, as well as their shelf lives. It proposes a new manner of determining the shelf live, along with new definitions for clarity.
While terms about shelf lives are used interchangeably, the article postulates the following terms (pg 913):
- True Shelf Life: The actual life of the product. This quantity is usually unknown.
- Both batches (e.g a bottle of pills) and individual products (e.g. a single tablet) have true shelf lives;
- True shelf lives within and among batches will vary;
- Estimated Shelf Life: The estimate of the true shelf life.
- Determined by a stability study
- Supported Shelf Life: A “suitably conservative estimate of the true product shelf life”.
- Maximum Shelf Life: An extrapolation of the estimated shelf life based on the duration of stability study and ICH Q1E rules. For example, a drug with a 12-month stability study might have a max shelf life of 18 months (1.5 times).
- Labeled Shelf Life: “…the shorter of the supported shelf life and the maximum shelf life.”
A comparison between the two models for estimating the true shelf life. Fig. 3 (pg 916) illustrates the issue with waiting for the average trend of the batches to reach the “acceptance criteria”, or where the product is no longer usable. By then, a significant portion of the batches may already be past use.
Fig. 4. (pg 917) sets the labeled shelf life at the time when an allowable percentage of the batches have expired, thus ensuring that the true shelf life is longer than the labeled shelf life.