Buccal drug delivery is the administration of a therapeutic substance to the mucosal lining of the cheek for local action or absorption across the epithelium. A formulation contacts a moist surface exposed to saliva, tissue movement, and clearance into the gastrointestinal tract ^[1][2]. Drug release and mucosal permeation occur in sequence, while saliva can dilute dissolved material and reduce its residence time. Mucoadhesive polymers prolong contact through interactions with mucus and the underlying mucosal surface ^[1]. The epithelial barrier regulates passage from the formulation toward the vascularized tissue beneath it, so molecular size and physicochemical characteristics influence absorption ^[2]. Films, tablets, gels, and devices provide different arrangements for maintaining contact and controlling exposure ^[1][3]. Device-based approaches can also address the limited passage of therapeutic peptides across the mucosal barrier ^[3]. For biological macromolecules, preservation of activity and transport across intact tissue remain separate requirements that connect formulation behaviour with the amount reaching the local or systemic compartment ^[4].