Drug–excipient interactions and their affect on absorption

Excipient(s) are traditionally thought of as inert but they can have a tremendous impact on the ultimate pharmacological availability of a drug substance when added to a formulation. The magnitude of this effect will depend on the characteristics of the drug and on the quantity and properties of the excipients. The aim of this article is to identify the various physicochemical and physiological processes that can be altered by drug–excipient interactions and to explore mechanisms by which they might occur. The regulatory implications of drug–excipient interactions will also be discussed.