Formoterol thrice weekly does not result in the development of tolerance to bronchoprotection.

Background: Loss of bronchoprotection routinely follows regular treatment with beta2-agonists. There are no data on the effects on bronchoprotection for thrice weekly use of a beta2-agonist.

Methods: A double-blind, randomized, placebo controlled crossover trial was conducted to investigate the effects of thrice weekly administration of 12 microg of formoterol versus placebo on bronchoprotection against methacholine. As an expected positive control, formoterol 12 microg once daily was also evaluated.

Results: There was no significant difference versus placebo in the bronchoprotective effects of 12 microg of formoterol administered on day 8, following daily treatment for seven days or treatment every other day (analysis of variance P=0.34). However, a nonsignificant trend towards lower concentration of methacholine that caused a 20% fall in forced expiratory volume in 1 s developed only following the daily formoterol dosing.

Conclusions: Thrice weekly dosing does not result in the development of tolerance to bronchoprotection against the direct acting stimulus methacholine.