Bronchial responsiveness during regular fenoterol therapy: four months prospective study.

Effects of a regimen of regular high dose beta agonist aerosol as sole therapy (fenoterol 400 micrograms qid) on FEV1 and bronchial responsiveness to methacholine provocation were examined monthly in 16 atopic moderately severe asthmatic subjects in an open uncontrolled four months study. Eleven completed the trial, four dropped out on account of severe acute asthma and one with muscle tremor. Overall there was a small significant drop of mean prebronchodilator FEV1 after one month of 0.27 L (95% confidence interval 0.12, 0.42) but not significant thereafter. The increase of bronchial responsiveness (mean decrease of PD20 of 0.50 doubling doses of methacholine) by the end of month four did not reach statistical significance. Our study which explored potentially adverse effects of this beta agonist regimen showed only small changes of doubtful clinical significance. Drop outs due to acute asthma complicate studies such as this and make conclusions difficult.