1. Particle Size:
Particle size greatly influences where in the respiratory tract the drug will deposit. Particles between 1-5 µm are optimal for deep lung deposition.
2. Breathing Pattern:
Deep and slow inhalation followed by a breath-hold ensures better deposition in the alveoli.
3. Airway Conditions:
Diseases like asthma or COPD can alter the airway geometry and mucus properties, affecting drug deposition and absorption.
4. Formulation Properties:
The use of certain excipients or the pH of the formulation can influence drug solubility and stability, which in turn can affect absorption.
5. Device Type:
The type of inhaler device (e.g., metered-dose inhaler, dry powder inhaler, nebulizer) can influence the particle size distribution and the velocity of the emitted dose, affecting deposition patterns.
6. Mucociliary Clearance:
The cilia in the bronchial region move mucus (and entrapped particles) upwards towards the throat, which can lead to clearance before absorption.
