Aerosol Performance and Stability Characteristics of Spray-Dried Tobramycin Excipient Enhanced Growth Inhalation Powder Formulations

Xiangyin Wei, Anubhav Kaviratna, Ruba S. Darweesh, P. Worth Longest, Michael Hindle

Despite advances in aerosol delivery with devices such as the TOBITM PodhalerTM, there is still room to improve the antibiotic dose delivered to the lungs, especially if powder inhalers are to be used for pediatric patients. The excipient enhanced growth (EEG) technology enables high efficiency delivery of powder aerosols even at low inhalation flow rates. This study sought to characterize the aerosol performance and stability of new tobramycin EEG (TOB-EEG) formulations. TOB-EEG powders were spray dried and their chemical stability evaluated following storage at ambient temperature and low humidity conditions for 10 months. TOB-EEG formulations were aerosolized following exposure to ambient temperature and humidity for 15 minutes and following storage at ambient temperature and low humidity for 6 months. The primary particle size of TOB-EEG powders was assessed following storage at ambient temperature and low humidity for up to 15 months. There was no significant change in the tobramycin content (98.8% of the initial content) for a TOB-EEG mannitol formulation following 10 months storage. Results also showed that 15 minute exposure to ambient conditions for a TOB-EEG sodium chloride formulation did not affect its aerosolization characteristics. A small improvement in the dispersion properties was observed following 6 months storage, perhaps indicating it is important to remove residual moisture before packaging. The geometric primary particle size of TOB-EEG powders were similar (x50~1 μm) when tested following storage, suggesting the powders are stable over long-term when maintained in low humidity environments, as could be achieved with foil-wrapped capsules or other packaging methods.

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