Objective: To evaluate the efficacy, safety, and impact on asthma-specific quality of life of salmeterol, a highly selective, long-acting beta 2-agonist, compared with that of placebo (i.e., "as-needed" albuterol).

Study design: Randomized, double-blind, placebo-controlled, parallel-group, multicenter study.

Patients and methods: Five hundred thirty-eight nonsmoking symptomatic patients 12 years of age and older meeting American Thoracic Society asthma criteria were enrolled at 55 outpatient clinics; 443 patients completed the study. Patients were randomly assigned to treatment with either salmeterol aerosol 42 micrograms twice daily or placebo (as-needed albuterol) for 12 weeks. We assessed changes in quality of life using the Asthma Quality of Life Questionnaire (AQLQ). Efficacy measurements included daily peak expiratory flow (PEF) rate, daytime and nighttime asthma symptoms, results of pulmonary function tests, and supplemental albuterol use. Patients recorded their PEF rate, supplemental albuterol use, and asthma-related symptoms daily. Pulmonary function tests and AQLQ assessments were performed at baseline and after 4, 8, and 12 weeks of treatment. Safety measurements included vital signs, physical examination, and reports of clinical adverse events at baseline and after 4, 8, and 12 weeks of treatment.

Results: Mean changes from baseline in AQLQ global and domain scores were significantly greater in the salmeterol group compared with the placebo group (P < 0.001). Patients treated with salmeterol also had significant improvements in mean PEF rates, supplemental albuterol use, asthma symptom scores, and forced expiratory volume in 1 second compared with those given placebo. Both salmeterol and placebo were well tolerated and were not associated with any clinically significant changes in vital signs or physical examination findings.

Conclusions: Salmeterol 42 micrograms twice daily resulted in significantly greater improvements in asthma-specific quality of life, pulmonary function, and asthma symptoms compared with placebo (as-needed albuterol) in patients with moderate persistent asthma.