The effect of formulation variables and breathing patterns on the site of nasal deposition in an anatomically correct model.

Purpose: This study was conducted to evaluate the effect of formulation variables and breathing patterns on aerosol distribution in the nasal cavity.

Methods: Placebo nasal spray formulations containing 0.25% w/v Avicel CL611 (viscosity = 4 cP) and 2% w/v methylcellulose (MC; viscosity = 18.2 cP) were radiolabeled with (99m)Technicium. Following spraying into a silicone nose model, through which air was drawn at one of three constant rates (0, 10, and 20 L/min) or one of two breathing profiles (representing fast and slow inhalations), aerosol deposition in the model was quantified by gamma scintigraphy. Regional deposition was expressed as horizontal[inner, middle (h), outer] and vertical distribution [upper, middle (v), lower] in the nose model.

Results: Compared to 2% MC, Avicel CL611 significantly increased aerosol deposition in the middle (h) region of the nasal cavity under all breathing conditions, and in the inner region at 0 and 20 L/min and with a slow inhalation. The different breathing rates showed no effect on deposition of 2% MC. However, 10 L/min significantly increased the upper deposition of Avicel compared to 0 and 20 L/min.

Conclusions: Nasal sprays with a low viscosity provided greater surface coverage of the nasal mucosa than higher viscosity formulations. Changes in breathing profiles did not affect aerosol deposition in this nose model.