Efficacy and Safety Study of Acetylcysteine/Doxofylline 1200/400 mg Effervescent Tablet in the Treatment of Moderate-Severe COPD.

Inclusion Criteria: * Patients aged ≥40 years with moderate-severe COPD diagnosis according to the GOLD and on a therapeutic regimen for COPD for a year * Patients with post-bronchodilator FEV1/FVC ratio \<0.70 * Patients with post-bronchodilator FEV1≥30% and \<80% of predicted normal value. * 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 who have 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 drugs contain Acetylcysteine or Doxofylline or other mucolitics or xanthines * Patients who use mucolitic and/or xantines derivatives or ephedrine routinely. * Patients who use CPAP (continous positive airway measure), BiPAP (bilevel continous positive airway measure) or mechanical ventilation * History of chronic respiratory diseases except COPD. * Patients who had COPD exacerbation or lower respiratory track infections that required antibiotic, oral or parenteral corticosteroid treatment within 4 weeks prior to first visit. * Patients who have a history of myocardial infarction, hearth failure, acute ischemic coroner disease or severe cardiac arrhythmia requiring treatment within least 6 weeks. * History of significant or uncontrolled disease or operation that may preclude participant from participating in the study * Patients who have lung cancer * Patients who had lung volume reduction operation * Women patients who are pregnant or nursing * History of allergic rhinitis or atopy * Patients who have known serious prostatic hypertrophy or narrow-angle glaucoma requiring drug therapy * History of alcohol abuse.