Pressurized metered dose inhalers and add-on devices.

Metered dose inhalers (MDIs) which have a valve holding chamber plus a mouthpiece or mask have, in recent years, markedly improved the ease, speed and reliability of aerosol therapy for reversible airflow obstruction in adults, children and infants. MDIs, effective and easily accessible when patients are away from home, are the gold standard for the treatment of reversible airflow obstruction since they provide reliable, reproducible, effort-independent dosing, protection of their contents from environmental humidity and bacterial infection and at the same time are the most readily pocketable, efficient and least expensive aerosol therapy devices available. When combined with add-on devices they are also the most versatile delivery system because they are well suited to a variety of patients and virtually any therapeutic task. With our improved understanding of the importance of drug targeting to the site of action, the most important aspects of the relationship between particle size and drug deposition throughout the lower respiratory tract are discussed. This review also looks at add-on devices and training issues related to the proper co-ordination of drug delivery with inhalation, and reports on new technology and non-ozone depleting propellants. Copyright 2001 Academic Press