The Influence of Spray Properties on Intranasal Deposition

Abstract

While numerous devices, formulations, and spray characteristics have been shown to influence nasal deposition efficiency, few studies have attempted to identify which of these interacting factors plays the greatest role in nasal spray deposition. The deposition patterns of solutions with a wide range of surface tensions and viscosities were measured using an MRI-derived nasal cavity replica. The resulting spray plumes had angles between 29° and 80° and contained droplet sizes (D_v50) from 37–157 μm. Each formulation contained rhodamine 590 as a fluorescent marker for detection. Administration angles of 30°, 40°, or 50° above horizontal were tested to investigate the role of user technique on nasal deposition. The amount of spray deposited within specific regions of the nasal cavity was determined by disassembling the replica and measuring the amount of rhodamine retained in each section. Most of the spray droplets were deposited onto the anterior region of the model, but sprays with small plume angles were capable of reaching the turbinate region with deposition efficiencies approaching 90%. Minimal dependence on droplet size, viscosity, or device was observed. Changes in inspiratory flow rate (0–60 L/min) had no significant effect on turbinate deposition efficiency. Both plume angle and administration angle were found to be important factors in determing deposition efficiency. For administration angles of 40° or 50°, maximal turbinate deposition efficiency (30–50%) occurred with plume angles of 55–65°, whereas a 30° administration angle gave an ∼75% deposition efficiency for similar plume angles. Deposition efficiencies of ∼90% could be achieved with plume angles <30° using 30° administration angles. Both the plume angle and administration angle are critical factors in determining deposition efficiency, while many other spray parameters, including particle size, have relatively minor influences on deposition within the nasal cavity.