Effects of a beta(2)-agonist on airway hyperreactivity in subjects with cervical spinal cord injury

Study objective: Aerosolized ipratropium bromide or orally administered bac lofen or oxybutynin chloride (Ditropan) block methacholine-associated airwa y hyperreactivity in subjects with chronic cervical spinal cord injury (SCI ), whereas these agents do not inhibit airway hyperreactivity associated wi th the inhalation of histamine. The present study was performed to determin e whether pretreatment with a beta(2)-agonist attenuates airway hyperrespon siveness in these subjects. Participants: Subjects with chronic cervical SCI previously demonstrating a irway hyperreactivity were challenged with methacholine (n = 9) or histamin e (n = 16) alone and, on a separate day, 25 min following inhalation of neb ulized metaproterenol sulfate. Results: Inhalation of the beta(2)-agonist was associated with an increase in provocative concentration causing a 20% decrease in FEV1 (PC20) values ( geometric mean) from 1.01 +/- 2.76 to 20.54 +/- 6.24 mg/mL for methacholine and from 2.29 +/- 2.26 to 19.82 +/- 5.93 mg/mL for histamine, No correlati on was found between specific PC20 values for individual subjects and perce ntage improvement in FEV1 (liter) following inhalation of metaproterenol su lfate and between PC20 values and baseline FEV1 percent. Conclusion: These data, combined with findings that patients with chronic h igh cervical SCI experience increased breathlessness following exposure to exogenous agents, suggest that long-term prophylactic beta(2)-agonist thera py may reduce respiratory symptoms associated with airway hyperreactivity i n these patients.