The dose emitted from dry powder inhalers (DPI) is inhalation flow dependent and so varies with the peak inhalation flow (PIF) of a patient's inhalation maneuver (IM). Dose emission could also be affected by other IM parameters-the inhaled volume (Vin) and the initial acceleration rate of the IM (ACIM). We have adapted the compendial method for in-vitro DPI determinations so that inhalation profiles replace the inhalation square profile generated by a vacuum pump. These real-life patient inhalation profiles were measured when 18 COPD patients inhaled through an empty placebo Symbicort® Turbuhaler®. They have been used to identify the dose emission characteristics from a fixed dosed combination of 200 μg budesonide plus 6 μg formoterol Turbuhaler®. To isolate each inhalation parameter some profiles were modified to provide a further 9 profiles to study the influence of Vin and 27 to identify the effect of ACIM. The fine particle dose, total emitted dose and mass median aerodynamic diameter were significantly (p < 0.05) influenced by PIF (p < 0.05) whereas ACIM and Vin had only a small effect. The results show the value of this ex-vivo methodology to provide an insight into the dose that each patient would have inhaled during real-life use.
- Department of Pharmacy - Senior Lecturer
- School of Applied Sciences
- Pharmaceutics and Drug Delivery Centre - Member
- Microbial Therapeutics and Infection Control Centre - Associate Member
- Biorefinery Engineering and Bioprocessing Research Centre - Associate Member