ABSTRACT
For solid oral dosage forms such as tablets and capsules, the 1987 FDA stability guideline indicates that the characteristics of appearance, friability, hardness, color, odor, moisture, strength, and dissolution for tablets and the characteristics of strength, moisture, color, appearance, shape brittleness, and dissolution for capsules should be studied in stability studies. Some of these characteristics are measured based on a discrete rating scale. For example, an intensity scale of 0 (none) to 4 (severe) may be used for odor. A continuous response discredited by rounding is another example. The responses obtained from a discrete rating scale may be classified into acceptable (pass) and not acceptable (failure) categories, which results in binary stability data. Although in most stability studies, continuous responses such as potency are the primary concern, discrete responses such as appearance, color and odor should be considered for quality assurance or safety. For establishing drug shelf-life based on discrete responses, however, there is little discussion in either the FDA or the ICH stability guidelines.
