Effects of cromolyn sodium on lung function in asthmatic patients

INTERVENTION: 1. cromolyn 20 group: Patient must inhale powder content of a capsule of cromolyn sodium (20 mg) by spinhaler through mouth. 2. cromolyn 40 group: Patient must inhale 40mg powder of cromolyn sodium by spinhaler through mouth. 3. placebo group:Patient must inhale from a hollow and cleaned (dose not contain any drug) capsule of cromolyn sodium by spinhaler through mouth. Intervention 1: 1. cromolyn 20 group: Patient must inhale powder content of a capsule of cromolyn sodium (20 mg) by spinhaler through mouth. Intervention 2: 2. cromolyn 40 group: Patient must inhale 40mg powder of cromolyn sodium by spinhaler through mouth. Intervention 3: 3. placebo group:Patient must inhale from a hollow and cleaned (dose not contain any drug) capsule of cromolyn sodium by spinhaler through mouth. Treatment ‐ Drugs CONDITION: bronchial asthma. ; Predominantly allergic asthma Predominantly allergic asthma PRIMARY OUTCOME: FEV1. Timepoint: 15 min, 30 min, 60min after inhalation. Method of measurement: Spirometry test. FVC. Timepoint: 15min, 30min, 60min after inhalation. Method of measurement: spirometry test. MEF25%. Timepoint: 15 min, 30 min, 60min after inhalation. Method of measurement: Spirometry test. MEF50%. Timepoint: 15 min, 30 min, 60min after inhalation. Method of measurement: Spirometry test. MEF75%. Timepoint: 15 min, 30 min, 60min after inhalation. Method of measurement: Spirometry test. PEF. Timepoint: 15 min, 30 min, 60min after inhalation. Method of measurement: Spirometry test. SECONDARY OUTCOME: Adverse effects after inhalation of drug or placebo. Timepoint: each 15 min after inhalation, until 2 hours. Method of measurement: observation. INCLUSION CRITERIA: Inclusion critreia: subjects with documented diagnosis of asthma and reversible airflow obstruction; FEV1<80% of predicted value;in a stable condition with regard to asthma symptoms Exclusion criteria: acute attack of asthma; chronic disease such as heart disease; pateints with respiratory infection in last month; smoking