A 70-year-old man with moderate COPD (post-bronchodilator FEV₁ 55% predicted) presents to his GP with a 5-day history of increased cough, sputum volume and purulence, but no fever or signs of pneumonia. You decide antibiotic therapy is indicated. According to Therapeutic Guidelines (Antibiotic), which oral regimen is preferred first-line in the community setting?