Effect of powder inhaler design on drug deposition in the respiratory tract

Abstract

Disodium cromoglycate particles were labelled with pure γ-radiator, 99mTc, using the co-precipitation technique based on spray drying. Radioactive drug particles were mixed with lactose carrier and filled into hard gelatin capsules. Seven healthy volunteers inhaled drug doses using Spinhaler I.S.F., Berotec, and Rotahaler dry powder devices. The fractional deposition of drug particles in the upper airways and lung region were monitored using a gamma camera. The fraction of the dose retained in the powder inhaler was the smallest for I.S.F. and especially for Berotec inhalers. These devices have narrower air channel constructions with a smaller wall surface area than the Spinhaler and Rotahaler devices. Thus the sticking of the drug particles onto the plastic walls was less probable for the first-mentioned devices. The drug particles from all the dry powder inhalers seemed to be more able to follow the inspired air stream without depositing in the upper airways than previously documented for pressurized metered dose aerosols. I.S.F. and Berotec inhalers with narrow air channels gave the greatest lung deposition of the inhaled drug particles. Thus the design of the dry powder inhaler was noticed to have a remarkable effect both on the emptying of the capsules as well as on the redispersion of the powder mixture.