Nose as a route for drug delivery

Abstract

Intranasal administration of topical drugs has always been used for symptomatic relief or treatment of local nasal dysfunctions. However, over the last years, the use of the nasal route for drug delivery as a viable and promising alternative to conventional oral and parenteral routes has tremendously increased. Indeed, owing to the high vascularisation and large absorptive surface, the nasal respiratory mucosa is recognised as an appropriate site for systemic entry of drugs, circumventing the gastrointestinal and hepatic first-pass metabolism. Accordingly, the extent of absorption and bioavailability of several therapeutic compounds have been improved with intranasal delivery, particularly those that are poorly permeable and/or highly susceptible to enzymatic degradation, such as small polar molecules, peptides and proteins. On the other hand, the intranasal route has also demonstrated to have potential for targeting central nervous system-acting drugs since nasal olfactory region allows the direct connection between the nose and the brain. In this chapter, the most relevant in vivo and in vitro findings that support the advantages of the intranasal delivery of drugs with topical, systemic and central nervous system action are critically discussed as well as alternative approaches frequently adopted to overcome the high mucociliary clearance, the reduced residence time and the poor nasal permeability of some compounds. Throughout this overview, nasal therapeutic compounds already marketed and those currently under investigation are also highlighted.