Randomised placebo controlled trial of beta agonist dose reduction in asthma

Background-Many patients continue to take regular beta agonists, often at h igh doses, contrary to national and international guidelines. Some studies have suggested that this can worsen asthma control, but whether such patien ts can reduce their dose of beta agonist and whether they would benefit fro m this has not been determined. Reduction of beta agonist dose was studied in a placebo controlled parallel. group study. Methods-Following a run in period, 33 subjects with asthma taking regular b eta agonists were converted to an equivalent dose of terbutaline via a Turb ohaler. Two weeks later terbutaline was continued at the same dose or chang ed to placebo in two stages a week apart. The change over period was covere d by an increased dose of inhaled steroid to attenuate any immediate effect s of the change in dose. Subjects then attended weekly for six weeks for me asurement of forced expiratory volume in one second (FEV1) and the dose of methacholine that produced a 20% fall in FEV1 (PD20). Peak expiratory flow (PEF) and symptom scores were recorded twice daily throughout the study. Ex acerbations, lung function, bronchial responsiveness, bronchodilator respon se, beta agonist use, and symptoms were compared before and six weeks after reduction in the dose of beta agonist. Results-Twenty five of the 33 subjects completed the study; three patients in each group withdrew due to an asthma exacerbation. The median terbutalin e dose fell from 2500 to 500 mu g/day in the beta agonist reduction group a nd from 3000 to 2250 mu g/day in the control group. There were small non-si gnificant changes in FEV1, PEF, symptom scores and PD20 methacholine over t he course of the study. The FEV1 response to a beta agonist was greater in those who reduced their beta agonist dose than in the control group althoug h the final FEV1 achieved was the same. Conclusions-Patients with asthma taking high doses of beta agonists can red uce the amount of beta agonist they use without a significant change in the ir asthma control. There was no evidence of improved asthma control with be ta agonist dose reduction.