Estimating a single shelf-life for multiple batches
Pharmaceutical companies and manufacturers of food products are legally required to label the product's shelf-life on the packaging. For pharmaceutical products the requirements for how to determine the shelf-life are highly regulated. However, the regulatory documents do not specifically define the shelf-life. Instead, the definition is implied through the estimation procedure. In this paper, the focus is on the situation where multiple batches are used to determine a label shelf-life that is applicable to all future batches. Consequently, the short-comings of existing estimation approaches are discussed. These are then addressed by proposing a new definition of shelf-life and label shelf-life, where greater emphasis is placed on within and between batch variability. Furthermore, an estimation approach is developed and the properties of this approach are illustrated using a simulation study. Finally, the approach is applied to real data.