Aerosols in the Health Care Field

:: Section 4

Aerosolization of Dry Powder

Most passive dry powder dispensing systems require the use of a carrier substance (lactose or glucose) mixed into the drug to enable the drug powder to more readily flow out of the device. Reactions to lactose or glucose appear to be fewer than reactions to the surfactants and propellants used in pressurized MDIs, even though the amount of carriers is substantially greater than that of the drug and can represent 98% or more of the weight per inhaled dose in some blends.

DPIs create aerosols by drawing air through an aliquot of dry powder. The powder contains either micronized (< 5 µm in diameter) drug particles bound into loose aggregates, or micronized drug particles that are loosely bound to large (> 30 µm in diameter) lactose or glucose particles. Micronized particles adhere to each other and to most surfaces, and the addition of the larger carrier particles decreases interparticulate forces in the micronized drug powder so that separation into individual respirable particles (deaggregation) occurs more readily. Thus, carriers aid the flow of the drug powder from the device. Usually, the drug particles are bound to carrier particles and are stripped from the carrier particles by the energy provided by the patient's inhalation.

Reference

Dhand R. and Fink J. : Dry Powder Inhalers, Respiratory Care 44: 940, 1999.