This is an open-label, randomized, cross-over, active-controlled study to evaluate the efficacy and safety effects using Meptin® Swinghaler and Ventolin® MDI in stable asthma patients.

Inclusion Criteria:

1. Male or females outpatients aged ≥ 16 years old with stable mild to moderate persistent asthma; Stability was assessed the patient remained in the same severity class (mild, moderate) and had no acute exacerbations by investigator judgment during the past 14 days;

2. Pulmonary function test:

   • Improvement ≥12% reversibility in FEV1 or FVC following administration of an inhaled β2-agonist before the study or ;
   • Positive result of Broncho-provocation test (PC20 ≤ 32 mg/ml) before the study.

3. Baseline forced expiratory volume in one second 60% ≤(FEV1)≤ 90% of predicted value on entry of the study;

Exclusion Criteria:

1. Hypersensitivity to β2-agonist or lactose;
2. Hospitalization due to asthma during the previous 3months;
3. Respiratory tract infection requiring treatment with antibiotics in the previous 4 weeks;
4. Oral or systemic corticosteroids in the previous 4weeks;
5. Inadequately controlled hyperthyroidism;
6. Severe hepatic or renal or cardiovascular disease as judged by the investigator;
7. Patients receive an investigational drug within 30 days prior to admission to the study;
8. Patients with significant alcohol, drug or medication abuse as judged by the investigator;
9. Females who are pregnant or breast-feeding; (exception: Females of child-bearing age might be included, if in the opinion of the investigator, they are using adequate contraceptive precautions).