Drug deposition of pressurized inhalation aerosols II. Influence of vapour pressure and metered volume

Abstract

The influence of vapour pressure and metered dose volume on drug deposition was tested using terbutaline sulphate pressurized aerosols with the conventional Bricanyl actuator and an attached tube. In each test the nine healthy volunteers inhaled eight doses at 1 min intervals coordinated with the dose firing. The amount of drug deposited in actuator, tube and mouth was determined spectrophotometrically. It was found that the increase in vapour pressure from 374 kPa to 502 kPa resulted in a significantly higher deposition of drug in the actuator but in a significantly lower deposition in the tube, in the mouth and for the net total loss in actuator, tube and mouth. An increase in metering volume from 25 or 50 μl to 100 μl resulted in a significantly higher deposition of drug in the actuator, in the tube and for the net total loss in actuator, tube and mouth. In order to obtain a high availability of drug to the airways the metering volume of the pressurized aerosol should be low and the vapour pressure high.