Long-acting beta2-agonists versus placebo in addition to inhaled corticosteroids in children and adults with chronic asthma

Background Long-acting inhaled beta 2-adrenergic agonists are recommended as 'add-on' medication to inhaled corticosteroids in the maintenance therapy of asthmatic adults and children aged two years and above. Objectives To quantify in asthmatic patients the safety and efficacy of the addition of long-acting beta 2-agonists to inhaled corticosteroids on the incidence of asthma exacerbations, pulmonary function and other measures of asthma control. Search strategy We identified randomised controlled trials (RCTs) through electronic database searches (the Cochrane Airways Group Specialised Register, MEDLINE, EMBASE and CINAHL), bibliographies of RCTs and correspondence with manufacturers, until April 2004. Selection criteria RCTs were included that compared the addition of inhaled long-acting beta 2-agonists to corticosteroids with inhaled corticosteroids alone for asthma therapy in children aged two years and above and in adults. Data collection and analysis Studies were assessed independently by two review authors for methodological quality and data extraction. Confirmation was obtained from the trialists when possible. The primary endpoint was rate of asthma exacerbations requiring systemic corticosteroids. Secondary endpoints included pulmonary function tests (PFTs), symptom scores, adverse events and withdrawal rates. Main results Of 594 identified citations, 49 trials met the inclusion criteria: 27 full-text publications, one unpublished full-text report and 21 abstracts. Twenty-three citations (21 abstracts and two full-text publications) provided data in insufficient detail, 26 trials contributed to this systematic review. All but three trials were of high methodological quality. Most interventions (N = 26) were of four-month duration or less. Eight trials focused on children and 18 on adults, with participants generally symptomatic with moderate airway obstruction despite their current inhaled steroid regimen. If a trial had more than one intervention or control group, additional control to intervention comparisons were considered separately. Formoterol (N = 17) or salmeterol (N = 14) were most frequently added to low-dose inhaled corticosteroids (200 to 400 mu g/day of beclomethasone (BDP) or equivalent). The addition of a daily long-acting beta 2-agonist (LABA) reduced the risk of exacerbations requiring systemic steroids by 19% (relative risk (RR) 0.81, 95% CI 0.73 to 0.90). The number needed to treat for one extra patient to be free from exacerbation for one year was 18 (95% CI 13 to 33). The addition of LABA significantly improved FEV1 (weighted mean difference (WMD) 170 mL, 95% CI 110 to 240) using a random-effects model, increased the proportion of symptom-free days (WMD 17%, 95% CI 12 to 22, N = 6 trials) and rescue-free days (WMD 19%, 95% CI 12 to 26, N = 2 trials). The group treated with LABA plus inhaled corticosteroid showed a reduction in the use of rescue short-acting beta 2-agonists (WMD -0.7 puffs/day, 95% CI -1.2 to -0.2), experienced less withdrawals due to poor asthma control (RR 0.5, 95% CI 0.4 to 0.7) and less withdrawals due to any reason (RR 0.9, 95% CI 0.8 to 0.98), using a random-effects model. There was no group difference in risk of overall adverse effects (RR 0.98, 95% CI 0.92 to 1.05), withdrawals due to adverse health events (RR 1.29, 95% CI 0.96 to 1.75) or specific adverse health events. Authors' conclusions In patients who are symptomatic on low to high doses of inhaled corticosteroids, the addition of a long-acting beta 2-agonist reduces the rate of exacerbations requiring systemic steroids, improves lung function, symptoms and use of rescue short-acting beta 2-agonists. The similar number of serious adverse events and withdrawal rates in both groups provides some indirect evidence of the safety of long-acting beta 2-agonists as add-on therapy to inhaled corticosteroids.