ABSTRACT
Transmucosal nasal delivery is a promising drug delivery option where common drug administrations, such as intravenous, intramuscular, or oral are inapplicable. Recently, it has been shown that many drugs have better bioavailability by nasal route than the oral route. This has been attributed to rich vasculature and a highly permeable structure of the nasal mucosa coupled with avoidance of hepatic first-pass elimination, gut wall metabolism and/or destruction in the gastrointestinal tract. The physiology of the nose presents obstacles, but offers a promising route for non-invasive systemic delivery of numerous therapies and debatably drug delivery route to the brain. Intranasal microemulsions, gels and microspheres have gained increased interest in recent years as a delivery system for protein and peptides through the nasal route. Thus this review focuses on nasal drug delivery, various aspects of nasal anatomy and physiology, nasal drug absorption mechanisms, various nasal drug delivery systems, and their applications in drug delivery.