Oral Mucosal Absorption: Mechanisms, Methods, and Challenges in Drug Delivery

This review focuses on the mechanisms and methods involved in oral mucosal absorption, with a particular emphasis on drug delivery systems. It begins by discussing the protective role of saliva in the oral cavity, highlighting its importance in maintaining the health of the oral tissues and facilitating drug delivery. The review then delves into the mechanisms of oral mucosal absorption, including passive diffusion, which is the primary mechanism for drug transfer across the oral mucosa. It also explores the use of hydrophilic polymeric matrices as vehicles for oral transmucosal drug delivery systems, which are favored due to the water-rich environment of the oral cavity. The review further discusses the methods used to assess oral mucosal permeation, including both in vivo and in vitro approaches. In vivo methods, such as the buccal absorption test, are used to determine the bioavailability of drugs via this route, while in vitro methods are employed for high-throughput permeability screening. The review concludes by addressing the challenges and limitations associated with oral mucosal drug delivery, such as the difficulty in studying regional variation in drug absorption and the limitations of in vitro permeability models in predicting in vivo situations.