Nasal delivery systems and their effect on deposition and absorption.

Due to nasal anatomy and physiology, with a non-ciliated area in the anterior part of the nasal cavity and a ciliated region in the more posterior part of the nose, the site of deposition is of importance for the nasal mucociliary clearance and retainment of a formulation in the nose. Many drug delivery devices for nasal application of liquid, semisolid and solid formulations were investigated in respect to their deposition in the nasal cavity. The site of deposition and the deposition area depend on several parameters which are related to the delivery device, such as mode of administration, particle size of the formulation and velocity of the delivered particles. Several in vitro and in vivo methods have been used to study distribution and clearance of intranasally delivered therapeutics. The relationship between deposition, absorption and related bioavailability of the nasally applied formulation has been shown.