Drug–Excipient Interaction and Incompatibilities

Pharmaceutical excipients are traditionally considered as pharmacologically inert substances, but, can also actively participate in drug–excipient interactions, viz., physical, chemical, and physiological, to compromise with the stability of the product and therapeutic role of the drug component(s) following drug decomposition. However, the magnitude of decomposition of the drug substance(s) highly depends on the chemical configuration, quantity of the drug, and properties of the used excipients. This chapter discusses different types of interactions between drugs and excipients with several possible mechanistic understandings behind it that can alter various physicochemical and physiological processes. Such interactions between drugs with excipients can occur throughout the formulation developmental process. However, physiological interactions cannot be predicted before administration by the patients. Nonetheless, recent emerging case studies have also been discussed in this chapter for a better understanding of the interactive reactions. Finally, this chapter emphasizes special analytical techniques to identify such interactions between drug and excipients along with its regulatory implications to promote optimum formulation development to obtain prime drug bioavailability without affecting release and dissolution.