Mucoadhesive Drug Delivery Systems: Principles, Polymers, Pharmaceutical Applications, and Recent Advances

Mucoadhesive drug delivery systems have emerged as an effective strategy to enhance drug residence time at mucosal surfaces and improve therapeutic efficacy. These systems function through interactions between mucoadhesive polymers and the mucus layer covering epithelial tissues, leading to prolonged retention, improved absorption, and enhanced bioavailability. Mucoadhesion is governed by mechanisms such as wetting, adsorption, and interpenetration of polymer chains, which are explained by theories including electronic, adsorption, diffusion, and fracture theories. Polymer characteristics such as molecular weight, chain flexibility, degree of cross-linking, and functional groups play a critical role in determining adhesive strength. Mucoadhesive systems offer advantages such as avoidance of first-pass metabolism, reduced dosing frequency, improved patient compliance, and site-specific drug delivery. Various mucosal routes, including buccal, nasal, ocular, vaginal, rectal, and gastrointestinal routes, have been explored for both local and systemic therapy. Natural and synthetic polymers are widely employed, with chitosan and its derivatives receiving particular attention due to their biocompatibility and strong mucoadhesive properties. Recent advancements focus on thiolated polymers, bio-inspired materials, and nano-based systems to enhance adhesion and controlled drug release. Although significant progress has been made, challenges related to formulation stability, standardization, and clinical translation remain. Overall, mucoadhesive drug delivery systems represent a promising approach for improving therapeutic outcomes.