Basics: Excipients Used in Nonsterile Compounding, Part 4: Antioxidants and Chelating Agents

Pharmaceutical formulation involves patient acceptability and compliance, ease of preparation, microbiological considerations, and chemical and physical factors affecting compatibility of all ingredients and stability. Physical factors such as light, heat, and humidity can trigger or accelerate undesirable chemical reactions such as oxidation, hydrolysis, decarboxylation, racemization, and photolysis, compromising drug stability. Many drug products and preparations are subject to oxidation, which can often be catalyzed by light, temperature, hydrogen ion concentration, presence of trace metals, or peroxides. Oxidation of a product may be manifested as an unpleasant odor or taste, discoloration or other change in appearance, precipitation, or even a slight loss of activity. Antioxidants are often introduced to improve the shelf life of pharmaceuticals along with suggested procedures to minimize oxidation. Often, chelating agents are added with antioxidants to bind with any trace metals present and enhance the stability of the formulation.