The primary objective of the study is to compare the tolerability of Symbicort® Turbuhaler® 160/4.5 μg 10 inhalations with terbutaline Turbuhaler® 0.4 mg 10 inhalations for 3 days on top of Symbicort® Turbuhaler® 160/4.5 μg 1 inhalation twice a day (bid) in adult asthma patients.