Influence of the moisture on the performance of a new dry powder inhaler.

An accelerated stability test was carried out on two prototypes of a new dry powder inhaler (DPI) to verify the influence of moisture uptake on the performance of the device. The prototypes were stored at 40 degrees C and 75% relative humidity (RH) for different storage times and their performance was assessed in terms of emitted dose and respirable fraction (Twin Impinger). At the same time intervals, the water content of the powder contained in the drug reservoir was evaluated using Karl Fischer's method. The respirable fraction was strongly influenced by the moisture content of the powder, on the contrary, the dosing precision and reproducibility is independent of this variable. The results show that a suitable protection from the external environment is necessary to prevent moisture uptake in the powder and the consequent loss of efficiency of the delivery device.