In Vitro and in Vivo Deposition of Drug Particles Inhaled from Pressurized Aerosol and Dry Powder Inhaler

Abstract

Disodium cromoglycate particles were labelled with a pure ζ-radiator 99mTc using a novel co-precipitation technique based on spray drying. Metered dose aerosols as well as a dry powder dosage form were prepared using these labelled drug particles. Fractional deposition of the drug particles was determined in vivo by means of gamma camera. Inhalation patterns of seven healthy volunteers were compared to deposition patterns evaluated in vitro using a modified cascade impactor. On average only 9 per cent of the aerosol dose deposited in a whole lung area and about 81 per cent in the upper airways of the volunteers. The in vitro results showed clearly greater deposition of the drug particles into the imitated bronchial and alveolar stages. The physiological factors of the human respiratory tract as well as the individual differences in the inhalation techniques seemed to have a significant influence to the deposition and aerodynamic behaviour of the inhaled drug particles. The in vitro results indicated, however, the similar differences between the two inhalation dosage forms as the in vivo evaluation did.