Level 1: Likely reliable evidence
Salmeterol (Serevent) and formoterol (Foradil Aerolizer) are two long-acting beta2-agonists that are FDA-approved for maintenance treatment of chronic obstructive pulmonary disease (COPD), including emphysema and chronic bronchitis.
A systematic review of 23 published and unpublished randomized placebo-controlled trials evaluated the efficacy of salmeterol or formoterol in 6,061 patients with stable COPD and poor reversibility to short-acting bronchodilators (Cochrane Database Syst Rev. 2006:CD001104). The review included 15 published trials and eight unpublished trials; six of the unpublished trials were not used in the primary meta-analyses because of insufficient data on inclusion criteria. Trials lasted a minimum of four weeks.
Based on 13 trials, salmeterol 50 µg twice daily has the most supporting evidence for efficacy. Compared with placebo, salmeterol was associated with a reduced number of patients having COPD exacerbations (20.3% vs. 27.8%, NNT 14), based on four good-quality parallel trials with 1,741 patients. Including data from unpublished trials suggested a smaller effect (NNT 24).
Another outcome evaluated was withdrawal due to lack of efficacy, which was significantly reduced with salmeterol (1% vs. 4%, NNT 34), based on five trials with 1,581 patients. Including data from unpublished trials also suggested a smaller effect (NNT 46). The use of short-term rescue medications was reduced by 40%-78% in six trials with 974 patients. Based on a meta-analysis of four trials with 253 patients, there was a mean reduction of 0.99 puffs per day. There was also a significant improvement in total, activity, and impact domain scores on the St. George’s respiratory questionnaire. There were no significant differences in six-minute walking distance in four trials with 659 patients. Evidence was inconsistent regarding the impact on dyspnea because the timing and setting of dyspnea evaluation varied across trials.