Deposition of sprayed particles in the nasal cavity.

Therapeutic effects of topically applied steroids is closely related to the deposition of sprayed particles. To clarify deposition in the nasal cavity, model experiments were undertaken using the gas and powder sprays. Deposits on the moistened filter paper which covered the surface of a nose model were assessed by absorbance of the extracts. The influence of the shape and the effect of continuous suction from the posterior outlet were also studied. When the nasal cavity was kept straight without any abnormal protrusions, the gas spray deposited more than 90% of particles. The amount was significantly lowered in the model of a concave septum with hypertrophic turbinates. The powder spray deposited approximately 75% of the original dose. This amount was more than 90% of actually sprayed particles because some loss was inevitable in spraying the powder. In general, the shape of the cavity more affected the deposition of the gas spray than the powder spray. This difference was probably due to the spray angle and to the size and speed of the aerosol particles. It was concluded that the powder spray was preferable to the gas spray with regard to the deposition in the nasal cavity.