Therapeutic aerosols 1--physical and practical considerations.

The inhaled route is a logical means of treating respiratory disorders since drugs may be delivered directly to the large surface area of the tracheobron- chial tree and alveoli. The value of inhalation treatment was recognised by ancient civilisations in India, China, and the Middle East, as well as by Hippocrates and Galen.' Since those times, and par- ticularly recently, inhalation treatment has increased greatly in sophistication, and the advantages of this route for the delivery of specific drugs have become well recognised. The drugs often begin to act very rapidly, and as a smaller dose can be used than with oral or intravenous delivery there is generally a reduction in the incidence of systemic side effects.