Randomised placebo controlled trial of β agonist dose reduction in asthma
- Dr TW Harrison.
- Received 24 June 1998
- Revision requested 3 September 1998
- Revised 19 October 1998
- Accepted 20 October 1998
Abstract
BACKGROUND Many patients continue to take regular β agonists, often at high doses, contrary to national and international guidelines. Some studies have suggested that this can worsen asthma control, but whether such patients can reduce their dose of β agonist and whether they would benefit from this has not been determined. Reduction of β agonist dose was studied in a placebo controlled parallel group study.
METHODS Following a run in period, 33 subjects with asthma taking regular β agonists were converted to an equivalent dose of terbutaline via a Turbohaler. Two weeks later terbutaline was continued at the same dose or changed to placebo in two stages a week apart. The change over period was covered by an increased dose of inhaled steroid to attenuate any immediate effects of the change in dose. Subjects then attended weekly for 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, bronchodilator response, β agonist use, and symptoms were compared before and six weeks after reduction in the dose of β agonist.
RESULTS Twenty five of the 33 subjects completed the study; three patients in each group withdrew due to an asthma exacerbation. The median terbutaline dose fell from 2500 to 500 μg/day in the β agonist reduction group and from 3000 to 2250 μg/day in the control group. There were small non-significant changes in FEV1, PEF, symptom scores and PD20 methacholine over the course of the study. The FEV1 response to a β agonist was greater in those who reduced their β agonist dose than in the control group although the final FEV1 achieved was the same.
CONCLUSIONS Patients with asthma taking high doses of β agonists can reduce the amount of β agonist they use without a significant change in their asthma control. There was no evidence of improved asthma control with β agonist dose reduction.
