Supercritical assisted atomization: a novel technology for microparticles preparation of an asthma-controlling drug

The objective of this study was to produce microparticles of a new asthma-controlling drug by supercritical assisted atomization (SAA), proposed as an alternative to conventional jet-milling process. SAA is based on the solubilization of supercritical carbon dioxide in a liquid solution containing the drug; the ternary mixture is then sprayed through a nozzle, and microparticles are formed as a consequence of the enhanced atomization. SAA process parameters studied were precipitator temperature, nozzle diameter, and drug concentration in the liquid solution. Their influence was evaluated on morphology and size of precipitated particles. Spherical particles with mean particle size ranging from 1 to 3 microm of the new anti-asthma drug were produced by SAA. The mass median aerodynamic diameter (MMAD) of the SAA micronized particles and of the conventional jet-milled drug was used to compare the results obtainable using the 2 techniques. Particularly, MMADs from 1.6 to 4.0 microm were obtained by SAA at the optimum operating conditions and by varying the concentration of the solution injected. MMAD of 6.0 microm was calculated for the jet-milled drug. SAA samples also exhibited narrower particle size distribution (PSD). A good control of particle size and distribution together with no drug degradation was obtained by SAA process.