Long-acting beta2-agonists for chronic obstructive pulmonary disease.

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is characterised by airflow limitation which is only partially reversible. Long acting beta2-agonists, effective in the management of asthma,are also recommended for COPD management so it is important to establish whether these drugs are effective in reducing COPD symptoms in view of the potential side effect and cost burden.

OBJECTIVES

To determine the effectiveness of long acting beta2-adrenoceptor agonists in improving lung function and quality of life and reducing dyspnoea in patients with COPD.

SEARCH STRATEGY

A search was carried out using the Cochrane Airways Group register. Bibliographies of identified RCTs were searched for additional relevant RCTs. Authors of identified RCTs were contacted for other published and unpublished studies. In addition, unpublished studies were also obtained from the pharmaceutical companies that manufacture long acting beta2- adrenoceptor agonists.

SELECTION CRITERIA

All randomised controlled trials over four weeks in duration comparing treatment with long-acting beta2-adrenoceptor agonists (salmeterol and formoterol) with placebo in patients with stable non-reversible COPD. Outcome measures included forced expiratory volume in one second (FEV1), peak expiratory flow rate (PEFR), symptom scores, six minute walk distance, quality of life scores, Borg scores for dyspnoea and rescue bronchodilator use.

DATA COLLECTION AND ANALYSIS

Data extraction and study quality assessment was performed independently by two reviewers. Where further or missing data were required, authors of studies were contacted.

MAIN RESULTS

Thirty three abstracts were identified as potentially relevant. Of these, four randomised controlled trials (RCTs) were included in this review. Two were parallel group studies of 16 week duration and two were cross-over studies with four week treatment arms. All four RCTs assessed the efficacy of salmeterol in COPD. In a 16 week study of salmeterol 50 mcg and 100 mcg twice daily treatment, a significant increase in FEV1 was seen in both treatment groups. The weighted mean difference (WMD) for the increase in FEV1 for the 50 mcg group was 0.10 litre (95% CI: 0.05;0. 15) and in the 100 mcg group the WMD was 0.12 litre (95% CI: 0.06; 0. 17 ). In the two cross-over studies of four weeks treatment, salmeterol 50 mcg twice daily treatment did not show significant increases in FEV1 (WMD = 0.04 litre, 95% CI: -0.06; 0.15). Similarly, morning and night time PEFR was not significantly improved with salmeterol treatment. In a 16 week study, disease-specific quality of life, measured using the St. George's Respiratory Questionnaire (SGRQ), showed a significant improvement after 50 mcg twice daily, but not after 100 mcg twice daily. This improvement exceeded the threshold for a clinically significant change with this questionnaire. General health status, as measured by the Medical Outcomes Short Form 36, did not improve in any of the eight components with either salmeterol dose. No significant difference was demonstrated in the mean change from baseline in the six minute walk distance (WMD = 1.9 metres, 95% CI: -15.4;19.3). Breathlessness was reduced in one study in patients receiving salmeterol 50 mcg twice daily group. Significantly more patients in this group had Borg scores for breathlessness less than three (a score of three indicating moderate dyspnoea) compared to the placebo treated group (Peto Odds Ratio = 0.60, 95% CI: 0.40; 0.88). Neither dose of salmeterol influenced the incidence of COPD exacerbations, (50 mcg: Peto Odds Ratio = 0.74, 95% CI: 0.47, 1.15) and (100 mcg: Peto Odds Ratio = 0.98, 95% CI: 0.64, 1.52).

REVIEWER'S CONCLUSIONS: Treatment of patients with COPD with long acting beta2-agonists produces only small increases in FEV1. In one study, a dose of salmeterol 50 mcg twice daily produced a reduction in breathlessness and a clinically significant improvement in quality of life. (ABSTRACT TRUNCATED)