Leukotriene receptor antagonists (LTRAs) reduce fractional exhaled nitric oxide (FENO) concentrations in children with asthma, but the effect of LTRA withdrawal on FENO and lung function is unknown. We will aim to study the effect of treatment and withdrawal of montelukast, a LTRA, on airway inflammation as reflected by FENO and lung function in children with asthma.

A double-blind, randomized, placebo controlled, parallel group study will be undertaken in 18 atopic children with mild persistent asthma who will be treated with oral montelukast (5 mg/day for 4 weeks) and 18 atopic children with mild persistent asthma who will receive matching placebo.

A follow-up visit will be performed 2 weeks after montelukast or placebo withdrawal.

Inclusion Criteria:

• Children 6 to 14 yrs old, step 1 and step 2 GINA (Global INitiative for Asthma) guidelines
• exhaled nitric oxide (NO) >20 PPB at visit 2
• symptoms more often than twice a day, FEV1 equal or higher than 80% of predicted value and reversibility equal or higher than 12% to salbutamol, or a positive provocation test with methacholine, or exercise
• no regular medication, inhaled short-acting beta-2 agonists for symptom relief

Exclusion Criteria:

• Patient is hospitalized
• Patient has FEV1 < 80% predicted on visit 1
• Patient has 2 or more nighttime awakenings for asthma per week or pef variability 30% or more
• upper respiratory infection in the previous 3 weeks
• treatment with glucocorticoids or LTRAs in the previous 4 weeks
• treatment with inhaled glucocorticoids for more than 4 weeks in the previous year