Adequate number of patients could not be reached in the relevant centers.

The aim of the current study is to compare the efficacy and safety of Salmeterol/Fluticasone 50/500 mcg Inhalation Powder treatment administered via Capsair twice daily and original product Seretide Diskus 500 mcg Inhalation Powder treatment twice daily in patients with moderate-severe COPD.

Spirometric measurements will be performed at 12 different time points at pre-treatment and post-treatment (5. min, 15. min, 30. min, 1. hr, 2. hr, 3.hr, 4.hr, 6.hr, 8.hr, 10.hr and 12.hr) during the treatment visits of 11-weeks study period.

The aim of the current study is to compare the efficacy and safety of Salmeterol/Fluticasone 50/500 mcg Inhalation Powder treatment administered via Capsair twice daily and original product Seretide Diskus 500 mcg Inhalation Powder treatment twice daily in patients with moderate-severe COPD.

Patients who met all the inclusion criteria will enter a 1-week run-in period with the length determine by the specific medication, during which their usual treatment will be stopped and they will receive salbutamol as required.

Following run-in period, patients will be randomly assigned to receive Salmeterol/Fluticasone 50/500 mcg as dry powder capsule for inhalation by Capsair or Salmeterol/Fluticasone 50/500 mcg as dry powder for inhalation by Diskus twice daily for 8-weeks treatment period.

Patients will be evaluated at 6 consecutive visits: baseline (enrollment), screening, treatment (treatment initiation, after 4 and 8 weeks of treatment) and after treatment (will carry out by telephone two weeks following the last dose of study medication).

Spirometric measurements will be performed at 12 different time points at pre-treatment and post-treatment (5. min, 15. min, 30. min, 1. hr, 2. hr, 3.hr, 4.hr, 6.hr, 8.hr, 10.hr and 12.hr) during the treatment visits of 11-weeks study period.

Safety will be assessed through vital signs, adverse events, serious adverse events and all cause mortality.

Inclusion Criteria:

• Patients aged ≥40 years with moderate-severe COPD diagnosis according to the GOLD (The Global Initiative for Chronic Obstructive Lung Disease) strategy
• Patients who have symptomatic stable moderate to severe COPD diagnosis with post-bronchodilator FEV1/ Forced Vital Capacity (FVC) <0.70, and FEV1 ≥30% and <80% of predicted normal value at screening visit
• Current smokers or ex-smokers with a smoking history of at least 10 pack-years
• Patients who have no exacerbation within last 4 weeks
• Females patients with childbearing potential using effective birth control method
• Patients whose medication unchanged within least 4 weeks
• Patients who has a capability of communicate with investigator
• Patients who accept to comply with the requirements of the protocol
• Patients who signed written informed consent prior to participation

Exclusion Criteria:

• History of hypersensitivity to long acting beta-2 agonists or corticosteroids
• History of asthma or significant chronic respiratory diseases (e.g., interstitial lung diseases, significant bronchiectasis, etc.)
• Patients who had COPD exacerbation or lower respiratory track infections that required antibiotic, oral or parenteral corticosteroid treatment within 4 weeks prior to screening visit or during run-in period
• Use of immunosupresants or systemic corticosteroids within least 4 weeks
• History of severe cardiac arrhythmia or myocardial infarction within less than 6 months
• Significant or uncontrolled disease that may preclude participant from participating in the study
• Diognosis of cancer
• History of lung volume reduction operation
• Patients vaccinated with live attenuated vaccines within 2 weeks prior to screening visit or during run-in period
• Women patients who are pregnant or nursing
• History of allergic rhinitis and atopy