Excipients as stabilizers.

Excipients are better known as promoters of degradation than as stabilizers of drug substances. This is not surprising. Functional groups or residues in excipients can have the propensity to interact with labile active ingredients, with attendant loss of molecular integrity or other changes in quality. Thus, the canon of work on excipients as stabilizers is not extensive. Nevertheless, possibilities exist to capitalize on our knowledge of how a drug substance degrades, and of the properties and composition of excipients, to convert unstable drugs into viable products. This article discusses such approaches to product stabilization.