A theoretical and experimental analysis of formulation and device parameters affecting solution MDI size...

Area of Science:

• Pharmaceutical Sciences
• Aerosol Science
• Drug Delivery

Background:

• Metered Dose Inhalers (MDIs) are crucial for drug delivery.
• Understanding particle size distribution is key for MDI efficacy.
• Formulation and device factors influence aerosol performance.

Purpose of the Study:

• To investigate the influence of formulation and device configurations on solution MDI particle size.
• To develop theoretical and experimental models for predicting residual particle size distribution.
• To correlate initial droplet size with residual particle size.

Main Methods:

• Aerodynamic size distribution tests were performed on actuated solution MDIs.
• Theoretical relationships were developed to link initial droplet and residual particle sizes.
• Experimental variables included ethanol concentration, propellant type, valve size, and actuator orifice diameter.

Main Results:

• Residual particle size distributions were log-normally distributed without a large particle mode.
• Residual particle size was proportional to nonvolatile concentration to the one-third power.
• Formulation and device parameters significantly affected initial droplet size, with some effects mitigated by deposition.

Conclusions:

• Theoretical and empirical equations can predict residual particle size distribution for solution MDIs.
• Deposition in the mouthpiece and USP inlet influences measured particle size.
• Ethanol concentration impacts initial droplet size more than residual particle size due to deposition.