The primary objective of this study is to assess the efficacy (bronchoprotection) and safety of single doses of BI 1744 CL inhalation solution (2, 5, 10 and 20 mcg) delivered via the Respimat® inhaler, in patients with intermittent asthma.

Inclusion criteria

1. Diagnosis of intermittent asthma according to Global Initiative for Asthma criteria
2. Non-smokers or ex-smokers who have not smoked for at least 1 year and have a smoking history of less than 5 pack-years
3. Forced Expiratory Volume in 1second greater than or equal to 80% predicted normal (Visit 1).
4. Bronchial hyperresponsiveness to inhaled methacholine with a provocative concentration of a methacholine causing a 20% fall in Forced Expiratory Volume in one second less than or equal to 8 mg/mL (Visit 1).
5. Be able to perform technically acceptable pulmonary function tests
6. Be able to inhale medication in a competent manner from the Respimat® inhaler
7. Must sign and date an informed consent consistent with International Conference on Harmonisation-Good Clinical Practice guidelines prior to participation in the trial, which includes medication washout and restrictions.

Exclusion criteria

1. Patients with a significant disease other than asthma
2. Patients with seasonal asthma or allergies whose participation in the trial will occur during the season for which they are allergic.
3. Patients with clinically relevant abnormal baseline haematology, blood chemistry, or urinalysis; all patients with a serum glutamic oxaloacetic transaminase > 80 IU/L, serum glutamic pyruvic transaminase > 80 IU/L, bilirubin >2.0 mg/dL or creatinine > 2.0 mg/dL will be excluded regardless of clinical condition
4. Patients with any of the following conditions: a diagnosis of hyperthyrosis or paroxysmal tachycardia (>100 beats per minute), a marked baseline prolongation of QT/QTc interval, a history of additional risk factors for Torsade de Pointes, a history of myocardial infarction, a diagnosis of clinically relevant cardiac arrhythmia, a history of cor pulmonale, known active tuberculosis, a malignancy for which the patient has undergone resection, radiation therapy or chemotherapy within the last five years (patients with treated basal cell carcinoma are allowed), a history of life-threatening pulmonary obstruction, a history of cystic fibrosis, clinically evident bronchiectasis, or a history of significant alcohol or drug abuse.
5. Patients who have undergone thoracotomy with pulmonary resection
6. Patients who are being treated with any of the following concomitant medications: medications that prolong the QT/QTc interval, oral beta-adrenergics, beta-blockers or monoamine oxidase inhibitors or tricyclic antidepressants.
7. Patients who have been treated with any respiratory medications (excluding short-acting beta-agonists) for control of their asthma symptoms within 3 months of the Screening Visit (Visit 1).
8. Patients who have taken an investigational drug within one month or six half lives (whichever is greater) prior to Screening Visit (Visit 1).
9. Pregnant or nursing women, or women of childbearing potential not using a highly effective method of birth control.