Rebound increase in bronchial responsiveness after treatment with inhaled terbutaline.
To investigate whether cessation of regular beta-agonist treatment results in an increase in bronchial responsiveness, two double-blind, randomised crossover studies were done. Subjects with mild asthma were investigated to determine the course of change in bronchial responsiveness, measured as the provocative dose (PD20) of histamine that caused a 20% fall in forced expiratory volume in 1 s after short-term and longer term treatment with an inhaled beta-agonist. In the first study in 8 subjects, 500 and 2000 micrograms terbutaline thrice in 1 day protected against histamine-induced bronchoconstriction, and the increase in PD20 compared with placebo remained high throughout the day and overnight. In the second study 8 subjects received placebo or terbutaline 750 micrograms thrice daily for 14 days. The protection afforded by terbutaline against histamine-induced bronchoconstriction on day 14 was less than that on day 1 by 40% in the morning and 82% in the afternoon. On day 15 PD20 was lower after stopping terbutaline than placebo, with a maximum difference of 1.5 (95% CI 0.6-2.5) doubling-doses of histamine 23 h after the end of treatment. Thus treatment with terbutaline for 1 day did not result in any rebound increase in bronchial responsiveness. Treatment for 2 weeks impaired the ability of terbutaline to protect against histamine-induced bronchoconstriction, and was followed by a rebound increase in bronchial responsiveness after cessation of treatment.
D000293:Adolescent; D000328:Adult; D001249:Asthma / Q000188:drug therapy / Q000503:physiopathology; D001980:Bronchi / Q000503:physiopathology*; D001985:Bronchial Provocation Tests; D002986:Clinical Trials as Topic; D004311:Double-Blind Method; D005260:Female; D005541:Forced Expiratory Volume; D006632:Histamine; D006801:Humans; D008297:Male; D008875:Middle Aged; D010919:Placebos; D011897:Random Allocation; D012107:Research Design; D012138:Respiratory Therapy; D013726:Terbutaline / Q000008:administration & dosage / Q000009:adverse effects*; D013997:Time Factors
D010919:Placebos; D006632:Histamine; D013726:Terbutaline