Tsz Yan Alice Fong, Mathura Thirugnanasampanthar, Teresa Iley, Mark Parry, Ben Forbes
Effective nasal drug delivery requires an understanding of the factors that govern spray performance and regional nasal deposition. This study evaluated the effects of inspiratory flow, formulation viscosity, and device configuration on spray characteristics and regional nasal deposition. Low- (0.9 cP) and high-viscosity (4.0 cP) formulations were delivered using pressure-swirl, soft mist, and a syringe-coupled soft mist configuration under modified actuation conditions. Regional nasal and inhaled deposition fractions were quantified using the Alberta Idealised Nasal Inlet coupled to the Next Generation Impactor, operated under resting (7.5 L/min) and sniff-like (30 L/min) inspiratory flow. The highest vestibular deposition fraction (59.1%) occurred under resting inspiratory flow for the high-viscosity formulation delivered by the pressure-swirl device, consistent with enhanced inertial impaction of larger droplets. The highest turbinate deposition fraction (84.1%) occurred under sniff-like inspiratory flow for the high-viscosity formulation delivered by the syringe-coupled soft mist configuration. The olfactory deposition fraction was minimal (≤ 1.1%) across all conditions. The pressure-swirl device produced larger droplets and greater vestibular deposition under resting inspiratory flow. The soft mist platform generated smaller droplets, while the syringe-coupled soft mist configuration achieved the highest turbinate deposition under sniff-like inspiratory flow. These findings suggest droplet inertia (modulated by formulation viscosity and device atomisation mechanism) and airflow-driven entrainment (modulated by inspiratory flow) govern regional nasal deposition.