Page 65 - Quality control of pharmaceuticals (07-PA 704)

retest period for the drug substance or a shelf life for the drug product and
recommended storage conditions.
The United States Pharmacopeia (USP 36/NF 31) provides definitions for five
general types of stability:

1. Chemical: each active ingredient retains its chemical integrity and labeled
potency, within the specified limits.

2. Physical: the original physical properties, including appearance, palatability,
uniformity, dissolution, and suspendability, are retained.

3. Microbiological: sterility or resistance to microbial growth is retained
according to the specified requirements. Antimicrobial agents that are present
retain effectiveness within the specified limits.

4. Therapeutic: the therapeutic effect remains unchanged.
5. Toxicological: no significant increase in toxicity occurs.

A. Chemical Stability:

Chemical stability of pharmaceutical molecules is a matter of great concern as it
affects the safety and efficacy of the drug product. The FDA and ICH guidance's
state the requirement of stability testing data to understand how the quality of a drug
substance and drug product changes with time under the influence of various
environment factors. Changes in drug stability can risk patient safety by formation
of a toxic degradation product(s) or deliver a lower dose than expected. Therefore,
it is essential to know the purity profile and behavior of a drug substance under
various environmental conditions. Knowledge of the stability of molecule helps in
selecting proper formulation and package as well as providing proper storage
conditions and shelf life, which is essential for regulatory documentation.

B. Stability testing methods: