The primary objective of this study is to confirm the efficacy (superiority) of Symbicort® Turbuhaler® 160/4.5 µg twice daily for 8 weeks in comparison to Pulmicort® Turbuhaler® 200 µg twice daily + Theolong® tablet 200 mg twice daily.

Inclusion Criteria:

• Diagnosis of asthma with a documented history of at least 6 months duration prior to Visit 1
• Prescribed daily use of an IGCS for >=12 weeks prior to Visit 1. The dose of IGCS must be 400 to 800 µg/day of Pulmicort® Turbuhaler® or corresponding dose of IGCS. The prescribed dose of IGCS should be constant for at least 4 weeks prior to Visit 1
• Prescribed daily use of sustained release theophylline for at least 8 weeks prior to Visit 1, or confirmed steady-state blood theophylline concentrations within the effective range (5-15 µg/mL) during 8 weeks prior to Visit 1. The prescribed dose of theophylline should be constant (400 mg/day) for at least 4 weeks prior to Visit 1

Exclusion Criteria:

• Any significant disease or disorder that may jeopardize the safety of the patient
• Respiratory infection, judged by the investigator(s) as an infection affecting the asthma, within 4 weeks prior to Visit 1
• Treatment with oral, parenteral or rectal GCS within 4 weeks prior to Visit 1

Additional inclusion and exclusion criteria will be evaluated by the Investigator