Basics: Excipients Used in Nonsterile Compounding, Part 3: Preservatives.

Preservative selection is a critical step in the preparation of a formulation to ensure its microbiological effectiveness and stability. A number of physicochemical factors must be considered when selecting a preservative, including concentration, solubility, and pH. A preservative must also be nontoxic, stable, compatible, inexpensive, and have an acceptable taste, odor, and color. It should also be effective against a wide variety of bacteria, fungi, and yeasts, and be free from incompatibilities. This article discusses some of the factors involved in selecting an appropriate preservative.