With nasal medications, non CFC sprays have been available for many years and won wide acceptance. They are already prescribed in greater quantities than the CFC sprays. These metered dose mechanical sprays of liquids containing solutions or suspensions of medicines are proved effective, therefore the loss of CFCs poses little threat. Inhaled asthma medications are different. Penetration of these drugs to the small airways where the swelling and bronchospasm cause the most trouble depends on creating a mist of fine droplets or particles five microns or less in diameter.
Any larger particle fails to travel well and simply lands in the mouth.
Liquid mechanical sprays or aerosol generators don't make very many such small droplets. Drug manufacturers have approached the problem of making fine particle measured doses of medication without CFCs in two ways. They have used finely divided powders or subsituted a non CFC propellant. Now that data have come in on these methods, it appears that they may be better for patients than CFC-MDIs. Dry powders were pioneered in Europe and have been available for some time there.