Effect of formoterol, a long‐lasting beta 2‐adrenoceptor agonist, against methacholine‐induced bronchoconstriction.

1. The effects of a new long‐acting inhaled beta 2‐adrenoceptor agonist aerosol formoterol (12 micrograms), on FEV1, and on methacholine‐ induced bronchoconstriction, were compared with those of terbutaline (250 micrograms) and placebo in 12 midly asthmatic subjects. 2. PC20, the concentration of methacholine needed to cause a 20% fall in baseline FEV1, was determined 2 and 5 h after formoterol, terbutaline and placebo on separate days. Baseline PC20 was determined on a different day. 3. Compared with terbutaline and placebo, formoterol hastened recovery from methacholine‐induced bronchoconstriction, and significantly increased mean PC20 (by 2.2‐ and 2.9‐fold at 2 and 5 h respectively). 4. Thus, formoterol has a protective effect against methacholine‐induced bronchoconstriction which lasts for at least 5 h.