Pulmonary Deposition Rate of Dry Powder Inhalers: The Relationship Between Device Structure and Drug Particle Size

Dry powder inhalers (DPIs) are widely used for delivering medication directly to the lungs, especially for asthma and COPD. A key factor for DPI effectiveness is pulmonary deposition rate, influenced by the inhaler’s design and drug particle size.

What is Pulmonary Deposition?

Pulmonary deposition refers to the percentage of inhaled drug particles that reach the lungs’ target areas. Higher deposition improves therapeutic outcomes by delivering more medication to bronchial and alveolar regions.

Device Structure Impact

• Airflow Dynamics: DPI design, including airflow pathways and resistance, affects particle velocity and dispersion. Optimized airflow helps break up powder particles for better lung delivery.

• Powder Dispersion: Mechanisms like cyclone chambers, impaction surfaces, or mesh screens aid uniform powder dispersion.

• Dose Consistency: Accurate dosing ensures predictable drug delivery and consistent pulmonary deposition.

Drug Particle Size Matters

• Optimal Size: Particles between 1–5 µm best penetrate deep lungs. Larger particles (>5 µm) deposit in upper airways, while smaller (<1 µm) may be exhaled.

• Particle Shape & Density: These affect aerodynamic behavior and deposition efficiency.

• Agglomeration: Fine particles tend to cluster; effective DPI design must disperse these agglomerates for optimal delivery.

Synergy Between Device and Particle Size

Even with ideal particle size, poor DPI design can reduce deposition. Advanced inhalers improve dispersion, compensating for some variability in particle size.

Conclusion

Maximizing pulmonary deposition requires optimizing both DPI structure and drug particle size. This synergy enhances drug delivery efficiency, improves patient outcomes, and drives pharmaceutical innovation.