Randomised placebo controlled trial of β agonist dose reductionin asthma

BACKGROUND—Manypatients continue to take regular β agonists, often at high doses,contrary to national and international guidelines. Some studies havesuggested that this can worsen asthma control, but whether suchpatients can reduce their dose of β agonist and whether they wouldbenefit from this has not been determined. Reduction of β agonistdose was studied in a placebo controlled parallel group study.
METHODS—Followinga run in period, 33 subjects with asthma taking regular β agonistswere converted to an equivalent dose of terbutaline via a Turbohaler.Two weeks later terbutaline was continued at the same dose or changedto placebo in two stages a week apart. The change over period wascovered by an increased dose of inhaled steroid to attenuate anyimmediate effects of the change in dose. Subjects then attended weeklyfor six weeks for measurement 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.Exacerbations, lung function, bronchial responsiveness, bronchodilatorresponse, β agonist use, and symptoms were compared before and sixweeks after reduction in the dose of βagonist.
RESULTS—Twenty five ofthe 33 subjects completed the study; three patients in each groupwithdrew due to an asthma exacerbation. The median terbutaline dosefell from 2500 to 500 µg/day in the βagonist reduction group andfrom 3000 to 2250 µg/day in the control group. There were smallnon-significant changes in FEV₁, PEF, symptom scores andPD₂₀ methacholine over the course of the study. TheFEV₁ response to a β agonist was greater in those whoreduced their β agonist dose than in the control group although thefinal FEV₁ achieved was the same.
CONCLUSIONS—Patientswith asthma taking high doses of β agonists can reduce the amount ofβ agonist they use without a significant change in their asthmacontrol. There was no evidence of improved asthma control with β agonist dose reduction.