Dispersion of Drug Particles by Dry Powder Inhaler under Simulated Condition of Inhalation Pattern

Dispersion performance of Dry Powder Inhaler (DPI) depends largely upon the inhalation patterns of patients. In the present work, the inhalation patterns of healthy and COPD subjects with DPI were measured and a breathing simulator was constructed. Then, a measurement method with a gravitational settling chamber that allowed the particle size measurement without the dispersion during the measurement was proposed for the measurement of DPI dispersion performance under the simulated inhalation conditions. As a result, it was found that an increase in pressure drop of DPI markedly reduces the peak flow rate and that the dispersion performance of DPI is greatly affected by the inspiration patterns. The experimental data also suggested that Andersen impactor which is commonly used for the evaluation of dispersion performance of DPI is not suitable for this purpose because the dispersion of drug particles in the impactor is inevitable.