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 dr y powder inhaler (DPI) to verify the influence of moisture uptake on the pe rformance of the device. The phototypes were stored at 40 degrees C and 75% relative humidity (RH) for different storage times and their performance w as 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 respirab le 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 extern al environment is necessary to prevent moisture uptake in the powder and th e consequent loss of efficiency of the delivery device. (C) 1999 Elsevier S cience B.V. All rights reserved.