ABSTRACT
The Chinese were the first to use herbal preparations from the genus Ephedra, from which ephedrine was first derived approximately 5000 years ago (1). However, ephedrine was not recognized as a bronchodilator until the 1920s and became available in a nebulized form in 1929. Isoproterenol, a nonselective beta (β)-agonist that stimulates beta1-and beta2-receptors with equal efficacy, was synthesized in the 1940s. In 1961 the first selective β2-agonist, metaproterenol, was introduced for use in Europe. Since that time a number of short-acting (4-6 hours) and long-acting ( 12 hours) inhaled β2-agonists have become available (Table 1). Over the years there has been an increased emphasis on the development of more selective β2agonists with longer half-lives.
