The primary objective of this study is to examine efficacy and safety of tiotropium compared to plac ebo as add-on therapy in severe asthmatics according to GINA step 4 classification

Inclusion Criteria:

Outpatients of either sex, age 18 - 75 years, with at least a documented 5 year history of asthma, and a current diagnosis of severe, persistent asthma (GINA step 4), smoking history < 10 pack years and >= 1 year smoking cessation; Patients must be symptomatic

Exclusion Criteria:

Patients

• with a recent history (i.e., six months or less) of myocardial infarction,
• who have been hospitalized for heart failure (NYHA class III or IV) within the past year,
• with any unstable or life threatening cardiac arrhythmia or cardiac arrhythmia requiring intervention or a change in drug therapy within the past year,
• with malignancy for which the patient has undergone resection, radiation ther apy or chemotherapy within the last five years,
• who have undergone thoracotomy with pulmonary resection,
• with moderate to severe renal impairment (creatinine clearance = 50 mL/min)