Pilot Study to Assess the Effect of High Dose N-acetylcysteine (NAC) in Chronic Obstructive Pulmonary Disease (COPD) Patients

Inclusion Criteria: 1. Patients with documented COPD based on the following criteria: * Smoking history of at least 10 pack-years * Decreased Tiffeneau index (FEV1/(FVC \< 0.70) 2. Patients aged ≥ 40 years 3. Patients who stopped smoking since more than 1 month 4. Patients who present moderate COPD with an FEV1 between 50 and 80% of predicted (GOLD 2) 5. Patients should be treated according to GOLD guidelines Exclusion Criteria: 1. Unstable patients who developed an exacerbation during the last 8 weeks 2. Patients who are current smokers or stopped less than 1 month 3. Patients who are allergic to acetylcysteine or to another element of the product 4. Patients with phenylketonuria or an untreated active peptic ulcer 5. Patients with any stage kidney and/or heart insufficiency or hypertension 6. Patients already treated with NAC for more than 6 months or during the last 3 months 7. Patients on continuous treatment with oral, inhalation, intravenous or intramuscular corticosteroids 8. Patients who are pregnant or are breast-feeding 9. Patients who are treated with orally administered cephalosporins 10. Patients using supplements containing antioxidants as vitamins C or E