The effects of surface morphology on the aerosol performance of spray-dried particles within HFA 134a based metered dose formulations

The aim of this study was to produce fine particles with different corrugated degree of surface by spray-drying and to investigate the effect of surface morphology on in vitro aerosol performance of the particles within HFA 134a based metered dose formulations. Compositions of rizatriptan and scutellarin were spray-dried using different spray-drying parameters, and particles were suspended within HFA 134a. The surface morphology were determined using scanning electron microscopy (SEM), while the aerodynamic performance of MDIs was evaluated using a next generation pharmaceutical impactor. The surface morphology of spray-dried particles could vary from smooth to moderately corrugated, and to raisin-like depending upon spray-drying parameters and preparation compositions. In general, increasing inlet temperature, decreasing feed concentration and/or adding leucine to the feed solution tended to increase the corrugated degree of particle surface. Deposition results indicated that raisin-like particle based MDIs for all compositions of the two drugs produced significantly better aerodynamic performance in terms of fine particle fractions and mass median aerodynamic diameters relative to the formulations of the corresponding smooth or slightly corrugated particles when the particle compositions were the same. The present results demonstrated that wrinkled particles increased fine particle fractions within surfactant-free MDI formulations.