The kinetics of cohesive powder de-agglomeration from three inhaler devices

Purpose

The purpose of the current investigation is to understand the kinetics of de-agglomeration (k_d) of micronised salbutamol sulphate (SS) and lactohale 300 (LH300) under varying air flow rates (30-180 l min⁻¹) from three dry powder inhaler devices (DPIs), Rotahaler^® (RH), Monodose Inhaler^® (MI) and Handihaler^® (HH).

Results

Cumulative fine particle mass vs. time profiles were obtained from the powder concentration, emitted mass and volume percent <5.4 μm, embedded in the particle size distributions of the aerosol at specific times. The rate of de-agglomeration (k_d), estimated from non-linear least squares modelling, increased with increasing air flow rates. The k_dvs. air flow rate profiles of SS and LH300 were significantly different at high air flow rates. The k_d was highest from RH and lowest from MI. Differences in k_d between the devices were related to device mode of operation while the differences between the materials were due to the powder bed structure.

Conclusion

This approach provided a methodology to measure the rate constant for cohesive powder de-agglomeration following aerosolisation from commercial devices and an initial understanding of the influence of device, air flow rate and material on these rate constants.