What is first-line outpatient therapy for otherwise healthy adults with community-acquired pneumonia and no risk factors for drug-resistant pathogens?

• A. Azithromycin 500 mg daily for 5–7 days.
• B. Amoxicillin 1 g three times daily for 5–7 days (or doxycycline 100 mg twice daily).
• C. Amoxicillin-clavulanate plus macrolide.
• D. Levofloxacin 750 mg daily for 5 days.

Answer: (B)

The main idea is to use a narrow-spectrum antibiotic that effectively covers the most common outpatient-causing organism, Streptococcus pneumoniae, in a healthy patient with no risk factors for drug-resistant pathogens. High-dose amoxicillin fits this well because it provides strong pneumococcal activity at a dose (about 1 g three times daily) that achieves adequate drug levels to overcome typical resistance and is safe and practical for outpatient use. An acceptable alternative is doxycycline for those with penicillin allergy or preferences against beta-lactams.

Azithromycin alone is less favored here due to rising macrolide resistance in pneumococcus, which reduces its reliability. Pairing amoxicillin-clavulanate with a macrolide broadens coverage to beta-lactamase–producing organisms and atypicals, but this broader approach isn’t necessary for otherwise healthy outpatients and adds unnecessary cost and potential side effects. Fluoroquinolones like levofloxacin offer very broad coverage, including atypicals and resistant organisms, but their safety concerns and the goal of antibiotic stewardship make them a non–first-line choice in this population.

So the best first-line outpatient therapy is high-dose amoxicillin, with doxycycline as a reasonable alternative if needed.