Antibiotics in Chronic Obstructive Pulmonary Disease (COPD)

Inclusion Criteria: * Age above 50 years * History of smoking * History of COPD * Antibiotics for 24 hours * At least 2 of the following: dyspnoea, coughing with sputum, and sputum with purulence * Informed consent Exclusion Criteria: * Pneumonia * Antibiotics for more than 36 hours * Antibiotics for other infection * Prednisolone, more than 0.5 mg/kg body weight/24 hours for more than 3 days * Malignancy * Other pulmonary disease * Immune deficiency * Not able to tolerate doxycycline * Severe heart, liver or kidney disease * Epilepsia * Not stable 24 hours after hospital admission * Need for assisted ventilation