A 52-week, double-blind, randomised, multi-centre, parallel-group,Phase III study in patients 12 years and older with asthma, evaluating the efficacy and safety of Symbicort® (budesonide/formoterol) Turbuhaler® 160/4.5 μg ‘as needed’ compared with terbutaline Turbuhaler® 0.4 mg ‘as needed’ and with Pulmicort® (budesonide) Turbuhaler® 200 μg twice daily plus terbutaline Turbuhaler® 0.4 mg ‘as needed’