Randomized, Double‐Blind, Crossover, Clinical‐End‐Point Pilot Study to Examine the Use of Exhaled Nitric Oxide as a Bioassay for Dose Separation of Inhaled Fluticasone Propionate

This was a randomized, double-blind, crossover, clinical-end-point pilot study examining the hypothesis that inhaled fluticasone propionate decreases exhaled nitric oxide (eNO) concentrations within a week of beginning treatment and shows evidence of dose separation across the marketed dose range. Subjects had a ≥6-month history of asthma and screening eNO ≥60 parts per billion. At the start of each treatment period, eNO was ≥55 parts per billion, and forced expiratory volume in 1 second was ≥50% predicted. Subjects attended a clinic visit daily on consecutive mornings during each of 3 1-week treatment periods to measure eNO and receive once-daily doses of 100/50, 250/50, or 500/50 fluticasone propionate/salmeterol combination product (Advair® Diskus). Daily eNO value recorded was the highest of 3 measurements; 1 inhalation of treatment was then administered. Procedures were repeated for 3 treatment cycles, separated by 14-day minimum washouts. A total of 105 subjects were screened; 22 were randomized; and 17 completed all treatments. Mean percentage eNO decrease (standard deviation) from day 1 baseline for each treatment period was 36.6 (±18.7), 45.3 (±16.5), and 54.6 (±12.5) with Advair® 100/50, 250/50, and 500/50, respectively. Mean percentage decrease in eNO across each treatment (dose) was modeled using a mixed-model ANOVA. Although the overall treatment was significant (P = .0015), because of the relatively small sample size and within-subject variability, only the 100/50 vs 500/50 (P = .0003) and 250/50 vs 500/50 (P = .047) treatments were significantly different.