USING NANOPARTICLES AS FLOWABILITY ENHANCERS IN DRY POWDER FORMULATIONS (DPI)

API (active pharmaceutical ingredient) microparticles, which are used in dry powder formulations, have to meet special criteria. Particles exhibiting an aerodynamic diameter between 1 mu m-5 mu m are able to reach the deeper parts of the lungs. These microparticles are very cohesive and show poor flow properties, which leads to difficulties concerning volumetrically dosing. Mykhaylova [8] worked on an alternative DPI formulation, which avoided the use of coarse carriers. In our work the flow behaviour of the API was studied by mixing with different concentrations (0%, 0.5%, 2.5% and 12.5%) of Aerosil registered R972. The Aerosil registered acts as nanoparticulate spacer between the API particles and thereby reduces interparticle interactions and enhances flowability. Two different methods to prepare the mixtures were used namely a Turbula registered mixer and electrostatically supported mixing using liquid nitrogen as suspending medium. The theoretical/analytical model being the basis to calculate the appropriate microparticle/nanoparticle ratio was established by Bresges [9]. Adding spacers to cohesive powder particles yielded an increase in flowability. It was shown that even a minimal concentration of 0.5% of Aerosil registered R972 influenced the flow properties in a positive way. Increasing the Aerosil registered R972 concentration in order to further enhance the flowability was not successful. It was found that using the electrostatically supported mixing procedure resulted in better outcomes when compared with Turbula registered mixing. In conclusion, the use of nanoparticles was shown to improve the particles flowability. Unfortunately Aerosil registered R972 is not approved for use in DPI formulations which is the reason why there is need for substances which can be applied as alternatives. It is possible that the use of API nanoparticles as spacers will be of benefit as it will avoid any additional excipient.