The efficacy of muscarinic antagonists in asthma has been known since the early 1800s when inhalation of smoke from burning Datura stramonium leaves and roots became widespread in Britain as a treatment for obstructive airway disease (reviewed by Mansfield and Bernstein [1]). Once identified as the active agent, subsequent clinical studies were conducted with atropine [2], in turn replaced by the short-acting muscarinic antagonist (SAMA) ipratropium bromide due to better efficacy and lower systemic effects [3].
