Shelf lives of medication

The concept of a shelf life for a product is now quite widely accepted in modern life. They can be found on a huge number of consumables, from foods and cosmetics to slightly more surprising items like batteries and sterile products. For some items, there can be obvious cues as to when a product is no longer suitable for use, irrespective of their shelf life, such as when foods have spoiled. For other products their continued suitability for use may not be immediately apparent to human senses and we rely more on a stated date until which they are considered safe to use. Most pharmaceutical products fall into this latter category, where it can be hard to determine if they are suitable for use by sight or smell. The construction of shelf lives is an involved process that relies on the chemical analysis of products and statistical modelling (Capen et al, 2012) but ultimately relates to how fast a product degrades under expected conditions. The following calculations will run through a highly simplified scenario to demonstrate how a product changes over time and how this relates to its shelf life.