[Long-term effects of inhaled beta 2-agonists on bronchial hyperresponsiveness in asthmatics]

We examined the effects of two year's treatment of three inhaled beta 2-agonists (beta 2), such as salbutamol (S), procaterol (P) and fenoterol (F) on acetylcholine induced bronchial hyperresponsiveness (BHR) in mild approximately moderate asthmatics. When symptomatic use of beta 2 were less than 6 puffs/day, BHR was improved significantly with both S and P but was not with F. When more than 6 puffs/day, all three beta 2 did not show the improvement of BHR. Without the effect of corticosteroids, BHR was improved with S, and was partially improved with P in case of only less than 6 puffs/day, but was not improved with F unrelated to the inhaled puff number. Therefore, frequent use of beta 2 even if used only on demand was shown to worse BHR, asthmatics must be controlled to under the good condition of using beta 2 at least less than 6 puffs/day.