The effect of Montelukast on bronchial provocation tests and exhaled nitrix oxide levels in asthmatic patients

Background: Leukotriene antagonist therapy in asthmatic patients alleviates symptoms and improves exercise tolerance, however the effect of these drugs on bronchial firovocation tests and exhaled nitric oxide levels are less clearly established. Objective: To determine the effect, of montelukast treatment on airway hyperresponsiveness to exercise, methacholine and adenosine-5′-monophosphate and on exhaled nitric oxide levels in steroid-naive asthmatics. Methods: Following a 2 week run-in period, 20 mild to moderate asthmatics were enrolled in an open label 6 week trial of oral montelukast-sodium therapy. Bronchial hyperreactivity (exercise, methacholine and adenosine-5′-monophospnate challenges) and exhaled nitric oxide levels were measured before and after the 6 week period. Results: Montelukast treatment resulted in a significant improvement in exercise tolerance: median ΔFEV₁ 20.0% (range 0-50) prior to treatment vs. 15.0% (range 0-50) post-treatment (P = 0.029). A significant difference was also observed for exhaled NO following therapy: median NO 16.0 ppb (range 7-41) vs. 13.0 (range 4.8-26) (P = 0.016). No change was seen in baseline lung function tests (FEV₁ MEF₅₀) or in the bronchial responsiveness (PC₂₀) for methacholine and adenosine-5′-monophosphate. Conclusions: This study demonstrates that the leukotriene antagonist montelukast-sodium reduces bronchial hyperreactivity in response to exercise and reduces exhaled nitric oxide levels but has little effect on bronchial responsiveness to methacholine and adenosine challenges.