Application Note: Particle Characterization Of Metered-Dose Inhalers

Metered-dose inhalers (MDIs) are devices that deliver a specific quantity of drug to the lungs. The size and shape of the micronized drug greatly influence the deposition profile in the lungs of the patient. Although the compendial tests for MDIs are based on cascade impactors, microscopic analysis is recommended by regulatory guidance documents and delivers important information. Automated image analysis now facilitates quantitative particle size and shape distribution data that can prove valuable to both formulators and quality control efforts.

An MDI typically delivers a specific dose of a micronized drug by supplying a short burst of aerosolized medicine that is inhaled by the patient. It is commonly used to treat respiratory diseases such as asthma or chronic obstructive pulmonary disease (COPD). The medication in a metered dose inhaler is most commonly a bronchodilator, corticosteroid or a combination of those two.