Optimal Inhalation Flow Pattern from Turbuhaler Predicted by Laser Photometry

The emitted dose (ED) from most dry powder inhalers (DPIs) is almost independent of peak inspiratory flow (PIF) above a certain value, which is specific to the individual DPI. However, the ED of the Turbuhaler^® (TBH) increases linearly with PIF increments. This study investigated the powder clearance and clinical utility of TBH performance features by using the photo-reflection method (PRM), a type of laser photometry. Pulmicort^® (PLM) (containing budesonide only) and Symbicort^® (SMB) (drugs with lactose particles) were inspired with a ramp-up pattern of several PIF intensities using a vacuum pump. Time trajectories of particle release and PIF were then compared. The particle-release trajectories from both types of DPIs were similar, consisting of a sharp increment phase (∼0.15 seconds) followed by exponential decay. Both onset to the peak of particle-release time and particle-release times were not affected by PIF changes when the PIF was >40 L/min. EDs from both TBHs were linearly related to PIFs, and the slope of the regression equation for SMB was 2.4-fold larger than that of PLM. The peak of the released particles (PK_IED) was also linearly related to PIF. A linear relationship was also observed between ED and PK_IED in both TBHs, and these regression lines overlapped. EDs from the TBH were dependent on PK_IED. Therefore, rapid, initially strong, and deep inhalation should be advised while using the TBH. PRM could measure the fine and small amount of particles released from the TBH.