Stability of a pharmaceutical product may be defined as the capability of a particular formulation, in a specific container/ closure system, to remain within its physical, chemical, microbiological, therapeutic, and toxicological specifications at a defined storage condition.
Pharmaceutical products are expected to meet their specifications for identity, purity, quality, and strength throughout their defined storage period at specific storage conditions. Assurances that the packaged product will be stable for its anticipated shelf life must come from an accumulation of valid data on the drug in its commercial package. These stability data include selected parameters that, taken together, form the stability profile.
The stability of a pharmaceutical product is investigated throughout the various stages of the development process. The stability of a drug substance is first assessed in the preformulation stage. At this stage, pharmaceutical scientists determine the drug substance and its related salts stability/compatibility with various solvents, buffered solutions and excipients considered for formulation development.
Suitable analytical methods must be employed in order to ensure the likelihood that this assessment will be successful. Optimization of a stable formulation of a pharmaceutical product is built (using statistical design) upon the information obtained from the preformulation stage and continues during the formulation development stages.
The use of kinetic and predictive studies for establishing credible expiration dating for pharmaceutical products is now accepted worldwide. Scientifically designed studies using reliable, meaningful, and specific stability-indicating assays, appropriate statistical concepts, and a computer to analyze the resulting data are used to determine an accurate and realistic shelf life.