Purpose: To determine the effect ipratropium bromide nasal spray has on methacholine challenge testing for airway hyperresponsiveness.
Materials and methods: Ten subjects with known airway hyperresponsiveness to methacholine who had been clinically stable in the preceding 2 months participated in a randomized, double-blind, placebo-controlled, crossover study. Methacholine challenge testing was conducted on successive days: day 1 after pretreatment with aqueous 0.03% nasal ipratropium, and day 2 with normal saline solution placebo.
Results: The provocative concentration of methacholine causing a 20% fall in FEV1 (PC20) was higher after nasal ipratropium than after saline solution placebo (2.1 mg/mL vs 1.6 mg/mL, p = 0.02). This difference is equal to approximately one-half concentration difference, probably within the limits of reproducibility of the test.
Conclusions: Pretreatment with nasal ipratropium results in a small increase in PC20. Although this difference achieves statistical significance, it is probably not clinically significant.