Evaluation of different parameters that affect droplet-size distribution from nasal sprays using the Malvern Spraytec

The applicability of laser diffraction (Spraytec) for characterizing the droplet-size distribution (DSD) from nasal sprays was examined to understand the relationship between physical properties of nasal formulations and their spray characteristics. The impact of actuation force (3-7 kg), rheological properties from carboxymethylcellulose (CMC) and carbopol 934PNF, the influence of surfactant (Tween 80), actuation distance, and different nasal-pump designs on the aerosol DSD of nasal sprays were investigated using Spraytec((R)) with the eNSP actuation station (InnovaSystems, Moorestown, NJ). Spray-pattern analysis was performed by monitoring the emitted nasal spray containing a dye or a fluorescent marker. Parameters for DSD and spray pattern included: Dv(10), Dv(50), Dv(90), polydispersity, minimum and maximum diameters, plume area, and ovality. Increasing actuation distance from 1.5 to 6 cm from the laser beam decreased Dv(50) values by 17-27% for commercial nasal-spray products. Spray-pattern analysis revealed a power law relationship between viscosity and surface area for CMC formulations. However, this relationship could not be obtained for carbopol formulations, which was attributed to differences in their rheological behavior. The addition of surfactant (0.5-5% Tween 80) to a 2% CMC solution decreased the Dv(50) values (16-26%) and altered the rheological properties (e.g., changes in viscosity and appearance of the thixotropic system). Briefly, the characteristic of nasal aerosol generation is dependent on a combination of actuation force, viscosity, rheological properties, surface tension, and pump design. The Spraytec with the eNSP actuation station provides an efficient and reliable way of monitoring the effects of formulation variables on DSD from nasal aerosols.