One of the most widespread dry
powder fixed combinations used in
asthma and
chronic obstructive pulmonary disease (
COPD) management is
Symbicort(®) Turbuhaler(®). The aim of this study was to simulate the deposition distribution of both components of this
drug within the airways based on realistic airflow measurements. Breathing parameters of 25 healthy adults (11 females and 14 males) were acquired while inhaling through Turbuhaler(®). Individual specific emitted doses and particle size distributions of
Symbicort(®) Turbuhaler(®) were determined. A self-developed particle deposition model was adapted and validated to simulate the deposition of
budesonide (inhaled
corticosteroid; ICS) and
formoterol (long acting β2 agonist; LABA) in the upper airways and lungs of the healthy volunteers. Based on current simulations the emitted doses varied between 50.4% and 92.5% of the metered dose for the ICS, and between 38% and 96.1% in case of LABA component depending on the individual inhalation flow rate. This variability induced a notable inter-individual spread of the deposited lung doses (mean: 33.6%, range: 20.4%-48.8% for
budesonide and mean: 29.8%, range: 16.4%-42.9% for
formoterol). Significant inter-gender differences were also observed. Average lung dose of
budesonide was 29.2% of the metered dose for females and 37% for males, while
formoterol deposited with 26.4% efficiency for females and 32.5% for males. Present results also highlighted the importance of breath-holding after inhalation of the
drug. About a half of the total lung deposition occurred during breath-hold at 9.6s average breath-hold time. Calculated depositions confirmed appropriate lung deposition of
Symbicort(®) Turbuhaler(®) for both genders, however more effort for optimal inhalation technique is advised for persons with low vital capacity. This study demonstrated the possibility of personalized prediction of airway deposition of
aerosol drugs by numerical simulations. The methodology developed in this study will be applicable also to other marketed drugs in the future.