Deposition of Inhalants in the Human Respiratory Tract

Size distributions were determined of particles generated by two types of aerosol inhalers, using three different dosage forms, each of them containing another active substance. It was found that only 6% of inhaled particles deposit in the target region even though 90% of them reach this region. When holding the breath after dose aplication, the deposition efficiency may increase a little. Despite some differences between the individual dosage forms none of them proved to be too beneficial in terms of particle deposition efficiency in the target region. Measurements under various temperatures and relative humidities showed that all studied inhalants are hydrophobic; the measured size distributions essentially did not change even at high relative humidities simulating conditions in the real respiratory tract