Dose-response relationship and reproducibility of the fall in exhaled nitric oxide after inhaled beclomethasone dipropionate therapy in asthma patients.

STUDY
OBJECTIVES: The fractional concentration of exhaled nitric oxide (FENO) is a marker of asthmatic airway inflammation. We determined the dose response and the reproducibility of the FENO fall following inhaled beclomethasone dipropionate (iBDP) therapy in nonsteroid-treated asthmatic patients. STUDY
DESIGN: Study A: For four 1-week periods (period 1 to period 4), the following regimens were administered in sequential order to 15 nonsteroid-treated asthmatic patients: period 1, placebo; period 2, 100 microg/d of iBDP; period 3, 400 microg/D of iBDP; and period 4, 800 microg/d of iBDP. Spirometry, FENO, and provocative concentration of methacholine resulting in a 20% fall in FEV(1) (PC(20)) were measured at each of five visits (visit 1 to visit 5). Study B: During four periods, 12 nonsteroid-treated asthmatic patients received placebo treatment for 7 days (period 1), 200 microg/d of iBDP for 14 days (period 2), washout on placebo treatment until the FENO was within 15% of baseline (period 3), and 200 microg/d of iBDP for 14 days (period 4).
RESULTS: Study A: Mean FEV(1) rose progressively from 3.10 L (visit 1) to 3.41 L (visit 5; p = 0.001). All iBDP doses caused a significant FEV(1) rise compared to placebo treatment, but with no significant separation of doses using FEV(1). FENO geometric mean (95% confidence limits) fell progressively from 103.5 parts per billion (ppb) (78.5 to 136.7) to 37.4 ppb (29.1 to 48.0) from visit 1 to visit 5 (p = 0.001). All doses of iBDP resulted in a significant change in FENO from placebo treatment, but with significant separation of only the 100-microg and 800-microg doses by FENO. Geometric mean (95% confidence limits) PC(20) rose progressively from 0.01 mg/mL (0.00 to 0.19) to 0.48 mg/mL (0.01 to 8.1) from visit 1 to visit 5 (p = 0.002). All doses of iBDP resulted in a significant change in PC(20) from baseline or placebo treatment, but with no significant separation of active iBDP doses using PC(20). Study B: FENO fell from 111.56 ppb (80.3 to 155.1) to 66.3 ppb (49.2 to 89.5; p < 0.001) from period 1 to period 2, and from 110.2 ppb (79.3 to 153.1) to 61.7 ppb (42.9 to 88.8; p < 0.001) from period 3 to period 4. There were no significant differences between FENO in period 1 and period 3 (p = 0.83) or between period 2 and period 4 (p = 0.220).
CONCLUSIONS: FENO was superior to FEV(1) and PC(20) in separating doses of iBDP. The fall in FENO after two identical administrations of iBDP separated by placebo washout was highly reproducible.

RCT Entities:   Population Interventions Outcomes