Aerodynamic Size Distribution of Cromolyn Sodium at Ambient and Airway Humidity

The aerodynamic size distribution of cromolyn sodium was determined at ambient and high (98%) humidity using the single particle aerodynamic relaxation time analyzer. This instrument measures the aerodynamic size single, suspended solid particles and liquid droplets in the respirable size range. The measurement accommodates all properties such as density, shape and surface characteristics that affect aerodynamic behavior. Particle morphology under ambient humidity conditions was studied using scanning electron microscopy. Count median aerodynamic diameter increased from 1.40 to 1.52 micron (p < 0.05), and the mass median aerodynamic diameter increased from 2.31 to 3.02 micron (p < 0.005) when measured at ambient and high humidities. The total mass of 0.99 mg of active ingredient aerosolized at ambient humidity in the size range compatible with pulmonary deposition was approximately 5% of the total mass of active ingredient packaged in the capsule. The low mass of particle aerosolized in the size range appropriate for pulmonary deposition may explain the low estimated deposition of cromolyn reported by other investigators.