The review of nasal drug delivery system: The strategies to enhance the efficiency of intranasal drug delivery by improving drug absorption.

Nasal drug administration constitutes an efficient and non-invasive modality of drug delivery, and its distinctive physiological structure offers potentialities for treating a variety of diseases. To elevate the drug absorption and delivery efficiency, it is of paramount importance to delineate the transport routes and their enhancement mechanisms. Nevertheless, drug absorption pathways vary depending on the disease target, these variations present opportunities for targeted delivery and challenges for achieving precision. Hence, this review outlines the anatomical structure of the nasal cavity, and subsequently elaborates on the drug transport pathways within the nasal cavity and their influencing factors. Based on the distinct sites of drug action, diseases suitable for nasal drug administration are categorized into three types: systemic diseases, local nasal diseases, and central nervous system diseases. Grounded on multiple transport routes and their influencing factors, this review proposes strategies like optimizing formulation viscosity, using penetration enhancers, adding mucosal adhesives and improving delivery device, offering insights into future advancements in nasal drug delivery systems.