The interplay of formulation viscosity with device type and inspiratory flow provides an opportunity to target regional nasal deposition
Tsz Yan Alice Fong1, Teresa Iley2, Mark Parry2 & Ben Forbes1
1King’s College London, Institute of Pharmaceutical Science, London SE1 9NH, UK
2Intertek, Melbourn, UK
Summary
This study investigated the effect of formulation viscosity in two different device types on spray characteristics and regional deposition in the nasal cavity. The influence of inspiratory airflow on nasal deposition was also investigated. Low and high viscosity formulations of a model drug, caffeine, were produced by varying the concentration of carboxymethyl cellulose. The formulation was incorporated into a conventional pressure-swirl actuator represented by Aptar® CPS and a novel Medspray Rayleigh nozzle® with a Medspray nasal soft mist device (low viscosity formulation) or a syringe (high viscosity formulation). The generated spray characteristics were assessed by measuring plume geometry, droplet size distribution, and deposition in a nasal cast operated at two different airflows, mimicking resting conditions and a ‘sniff’. Initial results indicated that the Medspray nasal device was unable to spray the high viscosity formulation, so the actuator nozzle was used with a syringe instead. Using a standard set-up, plume geometry could only be measured with the Aptar device, with the higher viscosity formulation producing narrower and more circular plume, the droplet size was larger compared to the lower viscosity formulation. The spray from the higher viscosity formulation resulted in a lesser turbinates deposition; greater formulation fraction was recovered from the olfactory region compared to the lower viscosity formulation. Contrarily, the Medspray nozzle produced a smaller droplet size irrespective to formulation viscosity, which, like the Aptar device, deposited predominately in the turbinates. Greater airflow simulated ‘sniffing’, which facilitated greater turbinates deposition in the distal nasal cavity.