What are the recommended antibiotic regimens for treating CAP in otherwise healthy adults?

Recommended antibiotic regimens for treating community-acquired pneumonia (CAP) in otherwise healthy adults:

• For adults with low-severity CAP (CRB-65 score 0), the first-choice oral antibiotic is amoxicillin 500 mg three times daily for 5 days. Higher doses may be used as per BNF guidance.
• If there is a penicillin allergy or amoxicillin is unsuitable (e.g., suspicion of atypical pathogens), alternatives include oral doxycycline 200 mg on day 1, then 100 mg once daily for 4 more days (total 5 days), or oral clarithromycin 500 mg twice daily for 5 days. In pregnancy, oral erythromycin 500 mg four times daily for 5 days is recommended.
• For moderate-severity CAP (CRB-65 score 1 or 2) managed in the community, prescribe oral amoxicillin 500 mg three times daily for 5 days plus, if atypical pathogens are suspected, add oral clarithromycin 500 mg twice daily for 5 days or erythromycin in pregnancy. If penicillin allergic, use doxycycline or clarithromycin alone as above.

These regimens are based on expert opinion considering antibiotic activity against likely pathogens, safety, and antimicrobial resistance risk. Amoxicillin is preferred due to its efficacy against Streptococcus pneumoniae and low adverse effects. Macrolides and doxycycline cover atypical pathogens and are alternatives when amoxicillin is unsuitable.

Patients should be advised to seek medical advice if symptoms worsen rapidly, do not improve after 3 days, or if they become systemically very unwell. Expected symptom resolution timelines are: fever by 1 week, chest pain and sputum reduction by 4 weeks, cough and breathlessness by 6 weeks, most symptoms resolved by 3 months, and full recovery by 6 months.