This is 9 month, placebo-controlled, double blind, randomised trial using the oral leucotrienes receptor antagonist montelukast (5 mg) in 160 children with mild and moderate asthma age 6-14 year old, sensitive to house dust mite. There are two study groups: montelukast group 80 patients and placebo group 80 patients. All patients will receive budesonide in dose sufficient to control asthma symptoms and short-acting beta agonist as needed. Medication used in the study: montelukast 5mg, budesonide. There are 7 doctor's visits - one initial visit (June) and 6 follow-up visits. First visit is on the first day of asthma symptom and each follow-up visit is every 6 weeks. Children with full asthma control (as measured by exhaled NO) had administered 100 mcg lower dose of budesonide and children with not fully control asthma had administered 100 mcg higher dose of budesonide.

The most potent anti-inflammatory drugs in asthma are glucocorticosteroids. Corticosteroids, however have side effects and do not fully suppress the production or release of all inflammatory mediators. Amongst those less affected are cysteinyl leucotrienes, which are known to play a key role in asthma. Antileucotrienes have a bronchodilator and bronchoprotective potential and have thus became part of current treatment recommendations in asthma.

Owing to the beneficial effects of antileucotrienes and the efforts to keep steroid doses low, our study address the extent to which inhaled corticosteroids might be substituted or supplemented by these drugs. We used symptoms, frequency of exacerbation, exercise induced bronchoconstriction test, and exhaled NO during a stepwise reduction of steroid doses to assess the association between these variables and their relation to the patients' clinical benefit; we used airway hyperresponsiveness to assess inflammatory process in airways.

This is 9 month, placebo-controlled, double blind, randomised trial using the oral leucotrienes receptor antagonist montelukast (5 mg) in 160 children with mild and moderate asthma age 6-14 year old, sensitive to house dust mite. There are two study groups: montelukast group 80 patients and placebo group 80 patients. All patients will receive budesonide in dose sufficient to control asthma symptoms and short-acting beta agonist as needed. Medication used in the study: montelukast 5mg, budesonide. There are 7 doctor's visits - one initial visit (June) and 6 follow-up visits. First visit is on the first day of asthma symptom and each follow-up visit is every 6 weeks. Children with full asthma control (as measured by exhaled NO) had administered 100 mcg lower dose of budesonide and children with not fully control asthma had administered 100 mcg higher dose of budesonide.

Methods used in the study:

• doctor's exam
• asthma symptoms questionaire
• exhaled NO
• spirometry
• exercise induced bronchoconstriction test
• airway hyperresponsiveness test

End points:

• steroid doses sufficient to control asthma symptoms
• medium steroid dose/day times 6 month
• number of asthma exacerbations in 9 month period
• maximum fall of FEV1 in exercise induced bronchoconstriction test
• asthma symptoms scale and lung function
• number of patients with positive airway hyperresponsiveness test

Inclusion Criteria:

• Children with bronchial asthma

Exclusion Criteria:

• All other serious diseases