Evaluating Customized Antibiotic Duration (CDA) Strategy in Acute Exacerbations of COPD

The goal of this clinical trial is to learn whether a shorter course of antibiotics (7 days) works as well as the usual longer course (14 days) for adults admitted to hospital with a flare-up of chronic obstructive pulmonary disease (COPD), a long-term lung disease. The trial takes place at CDA Hospital Islamabad, Pakistan. The main questions it aims to answer are: * Do patients who take antibiotics for 7 days recover as well by Day 30 as patients who take them for 14 days? * Does the shorter course lead to fewer side effects and less antibiotic use, without more treatment failures, relapses or hospital readmissions? Researchers will compare a 7-day antibiotic course with the usual 14-day course to see if the shorter course is just as effective. Participants will: * Be assigned by chance (like flipping a coin) to take antibiotics for either 7 days or 14 days. Their doctor chooses which antibiotic to use. * Receive all other usual hospital care for their COPD flare-up. * Have check-ups about 3-5 days, 7 days, 14 days and 30 days after joining the trial, in hospital or by telephone, to record their symptoms, any side effects and any return to hospital. About 560 adults will take part.

Inclusion Criteria: * Adults aged 18 years or older. * Physician-diagnosed COPD, confirmed by post-bronchodilator spirometry (FEV1/FVC \< 0.70) where available, or by documented previous spirometry consistent with COPD. * A current acute exacerbation of COPD for which the treating physician judges antibiotic therapy to be necessary, with at least two of the three cardinal symptoms (increased dyspnoea, increased sputum volume, increased sputum purulence). * Able and willing to give written informed consent and to follow the study procedures and follow-up schedule. Exclusion Criteria: * A documented infection that requires a defined, longer antibiotic course, such as pneumonia with complications, an exacerbation of bronchiectasis, lung abscess or empyema. * Need for immediate admission to intensive care or for invasive mechanical ventilation at presentation. * Severe immunosuppression, for example neutropenia, active malignancy under chemotherapy, organ transplantation or advanced HIV infection. * Suspected or confirmed pulmonary tuberculosis, or another respiratory infection that needs a different antimicrobial approach. * Pregnancy or breastfeeding. * Previous enrolment in this trial, or current participation in another interventional trial in AECOPD. * Systemic antibiotic treatment for the current exacerbation started more than 48 hours before randomisation.