Aerosols and Aerosol Drug Delivery Systems: Basics and Beyonds

	2.03.2009 SPEAKER: Myrna Dolovich, P ENG: McMaster University, St Joseph's Healthcare MODERATOR: José G. Venegas, PHD: MGH, HMS, CIMIT

Forum Summary

An aerosol is a two-state system consisting of a gas in which either liquid droplets or solid particles are dispersed.  Some aerosols, such as cigarette smoke or a neighbor’s sneeze, can be dangerous if inhaled, but other aerosols are therapeutic.  Inhaled aerosols are widely used to treat respiratory diseases because this delivery system deposits a drug topically in the lungs and thus limits the systemic dose.  The major challenge facing researchers seeking to deliver drugs to the lungs using an aerosol is to make sure that the medication gets to where it is supposed to go.

The lungs are designed to exclude particles, so introducing many small particles into the lungs using an aerosol is inherently difficult.  Even if a patient’s inhalation technique is perfect, the deposition of particles can be limited by airway geometry.  Most particles used in aerosols range in diameter from 0.5 to 5 microns, and one recent study suggests that particle size can affect the body’s response to a given drug.  In practice, it is difficult to produce aerosols in which all the particles are the same size, and the size of a particle influences how long the particle will remain suspended in a gas.  Aerosols often do not work very well when delivered through ventilators, and the presence of disease can alter airway geometry and make it more difficult for particles in an aerosol to disperse throughout the lungs.

A number of new technologies have recently been developed to improve the effectiveness of inhalers, which can be classified as metered-dose inhalers, dry powder inhalers, or nebulizers.  Spacers are now used with many metered-dose inhalers to collect large particles that would normally deposit in the mouth or the back of the throat.  These spacers have little effect on the concentration of drug deposited in the lungs, but they reduce the total amount of the drug deposited in the body.  More recent technological advances include the introduction of dose counters, breath-actuation, dose metering, and electronic monitoring systems.  In the future, patient feedback should be a central part of the design process for drug delivery systems involving aerosols.   

 

Post a Comment