Abstract
The study aimed to investigate dose consistency and particle distribution from the dry powder inhalers Diskus and Turbuhaler. Full profiles of inhalation pressure versus time were recorded in 18 4 yr old and 18 8 yr old asthmatic children through Diskus and Turbuhaler inhalers. These data were used in an inhalation profile simulator to assess drug delivery from both a Diskus inhaler and a Turbuhaler inhaler, and in particular to assess the proportion of drug emitted in the coarse (>4.7 microm) and fine (<4.7 microm) particle size range from each type of inhaler. The inhalation profile more accurately represents the changes in flow rate over time through the device than the constant flow rate usually applied with an impactor alone. The aerosol cloud was released before the peak inspiratory effort had been achieved and accordingly the early part and not the peak of the inspiratory performance is a determinant of the quality of the aerosol. The mean (SD) amount of drug in large particles (>4.7 microm), fine particles (<4.7 microm) and very fine particles (<2.1 microm) in percentage of label claim from the Fluticasone Diskus was 72 (5), 15 (2) and 2 (1) from the 4 yr old children and 71 (3), 18 (2) and 2 (1) from the 8 yr old children, respectively. Similar particle fractions from the Budesonide Turbuhaler were 35 (9), 21 (10) and 7 (5) from 4 yr old children and 30 (7), 32 (9) and 12 (6) from 8 yr old children. In conclusion, the Diskus inhaler provides an improved dose consistency through the varying age groups and inspiratory flow performances when compared to the Turbuhaler in terms of the proportion of the dose emitted at each particle size. This improvement is at the expense of a low fine particle mass and a high proportion of coarse particles from the Diskus as compared with the Turbuhaler.
