Community-acquired pneumonia
Acute infectious involvement of lung parenchyma acquired outside a hospital setting or within the first 48 hours of admission. Typical pathogens include Streptococcus pneumoniae, Mycoplasma pneumoniae, Chlamydia pneumoniae, and Haemophilus influenzae.
ICD-10 J18.912 drugs
Also known as: CAP, Outpatient pneumonia
Drugs used for this condition
- AAmoxicillinFirst line · Penicillins with extended spectrumAmoxicillin is the first-choice antibiotic for non-severe community-acquired pneumonia in adults treated as outpatients who have no chronic comorbidity and no risk factors for MRSA (methicillin-resistant Staphylococcus aureus) or Pseudomonas: ATS/IDSA 2019 recommend 1 g three times daily for at least 5 days and until clinical stability, NICE NG250 (2025) recommends 500 mg three times daily (higher doses can be used) for 5 days. Amoxicillin does not cover atypical pathogens (Mycoplasma, Legionella, Chlamydophila), so NICE adds Clarithromycin when they are suspected. With chronic comorbidity, ATS/IDSA suggest Amoxicillin/clavulanate or a cephalosporin combined with a macrolide or Doxycycline, or a respiratory fluoroquinolone alone; severe pneumonia is treated in hospital with parenteral regimens. The short course is supported by meta-analyses (Tansarli 2018, Furukawa 2023) and by the El Moussaoui 2006 RCT, in which 3 days of Amoxicillin was non-inferior to 8 days in hospitalised patients with non-severe pneumonia. In children with non-severe pneumonia Amoxicillin is also first choice (NICE NG250, Spanish AEP/SEIP consensus 2015). Per the label, it is contraindicated in penicillin allergy and after anaphylaxis to another beta-lactam; for allergic patients NICE suggests Doxycycline or Clarithromycin. Avoid Amoxicillin if infectious mononucleosis is suspected (rash); antibiotic-associated colitis can occur; reduce the dose in severe renal impairment. In pregnancy it is used when benefit outweighs risk; small amounts pass into breast milk and the infant may develop diarrhoea or candidiasis. Interactions: Methotrexate (increased toxicity), oral anticoagulants (monitor prothrombin time), Allopurinol (more rash).
- AAmoxicillin + Clavulanic AcidFirst line · Fixed-dose combination: aminopenicillin plus beta-lactamase inhibitorCommunity-acquired pneumonia in adults: outpatients with comorbidities (heart, lung, liver or kidney disease, diabetes, alcohol dependence, cancer, asplenia) and inpatients outside the ICU. Per ATS/IDSA 2019, amoxicillin-clavulanate is a first-choice option for outpatients with comorbidities, always combined with a macrolide (azithromycin, clarithromycin) or doxycycline; for outpatients without comorbidities amoxicillin is preferred. NICE NG138 (2019) names amoxicillin-clavulanate with clarithromycin as first choice in high-severity pneumonia. The Spanish SEPAR 2020 guideline includes the drug in initial regimens for outpatients and non-ICU inpatients together with a macrolide. Adult dose: 875/125 mg every 12 h or 500/125 mg every 8 h (ATS/IDSA 2019); the Spanish SmPC gives 875/125 mg 2–3 times daily. Treat for at least 5 days and until clinical stability; reassess at 48–72 h, and if there is no response, reconsider the diagnosis and escalate. The 875/125 mg tablets are not recommended in severe kidney impairment (creatinine clearance below 30 ml/min). Contraindications (AEMPS SmPC, 4.3): penicillin allergy, anaphylaxis to other beta-lactams, and a history of jaundice or liver injury with amoxicillin-clavulanate. Possible cholestatic hepatitis (more often in men and older adults, with prolonged courses, sometimes after the course has ended), diarrhea up to C. difficile-associated colitis, and rash in infectious mononucleosis. Interactions: oral anticoagulants (higher INR), methotrexate (more toxicity), mycophenolate (lower levels), allopurinol (more rash); clarithromycin adds its own CYP3A4 interactions and QT prolongation risk. Pregnancy (4.6): only if the doctor considers it essential; during breastfeeding the infant may develop diarrhea and candidiasis.
- AAzithromycinFirst line · MacrolidesFirst-line when atypical etiology is suspected in community-acquired pneumonia – Mycoplasma, Chlamydophila, Legionella. Also used in penicillin-allergic patients. Per IDSA/ATS 2019, azithromycin is used in the outpatient setting combined with a beta-lactam; macrolide monotherapy is only a conditional recommendation valid where local pneumococcal macrolide resistance is below 25%. In Spain resistance is high, so empiric macrolide monotherapy is generally not advised (SEPAR).
- ACeftriaxoneFirst line · Third-generation cephalosporinsModerate-to-severe community-acquired pneumonia. IDSA/ATS 2019 and Spanish SEPAR 2024 position ceftriaxone 1–2 g once daily as the empiric backbone in hospitalized patients combined with a macrolide (azithromycin 500 mg or clarithromycin) or a respiratory fluoroquinolone (levofloxacin). Treatment duration 5–7 days with typical response. ICU patients receive 2 g/day.
- AClarithromycinFirst line · Macrolide antibioticClarithromycin is included in empirical regimens for community-acquired pneumonia in outpatient adults without comorbidities and risk factors for drug-resistant pneumococci. IDSA/ATS 2019 recommend macrolide monotherapy where regional S. pneumoniae macrolide resistance is below 25%. For inpatients the macrolide is combined with a beta-lactam. The 2018 Cochrane review confirms comparable efficacy of macrolides and beta-lactams in the outpatient group.
- ADoxycyclineFirst line · TetracyclinesAlternative to macrolides for atypical community-acquired pneumonia. Active against Mycoplasma pneumoniae, Chlamydophila pneumoniae, Legionella. Per IDSA/ATS 2019, doxycycline is an outpatient CAP monotherapy option in patients without comorbidities when a macrolide is not suitable. Dose is 100 mg twice daily.
- AErythromycinSecond line · Macrolide antibioticMacrolide for atypical-pathogen community-acquired pneumonia (Mycoplasma pneumoniae, Chlamydophila pneumoniae, Legionella). SEIMC prefers azithromycin or clarithromycin for tolerability; erythromycin remains an alternative.
- ALevofloxacinSecond line · Third-generation fluoroquinoloneSecond-line for community-acquired pneumonia. Dose 500–750 mg once daily for 5–7 days. IDSA/ATS 2019 and SEPAR 2024 set high-dose amoxicillin or amoxicillin + macrolide as first-line outpatient CAP. Levofloxacin is used in penicillin allergy, severe disease with resistant pneumococcus risk, or comorbidities (COPD, diabetes).
- AMoxifloxacinSecond line · Fourth-generation fluoroquinoloneSecond-line for community-acquired pneumonia in patients with β-lactam allergy or at risk of resistant pneumococcus. IDSA/ATS 2019 and SEPAR 2024 set high-dose amoxicillin or amoxicillin + macrolide as first-line outpatient CAP. Moxifloxacin (400 mg once daily for 5 days) is used in allergy or first-line intolerance, or with risk of resistant Streptococcus pneumoniae.
- BCefditoren pivoxilSecond line · Third-generation oral cephalosporinAlternative for non-severe outpatient community-acquired pneumonia. Dose 400 mg twice daily for 5 days. SEPAR 2024 first-line is amoxicillin 1 g three times daily, with azithromycin added when atypical pathogens are suspected. Cefditoren is used in confirmed amoxicillin resistance or allergy. Patients with severe pneumonia and risk factors need admission and parenteral therapy.
- BCefuroxime axetilSecond line · Second-generation oral cephalosporinAlternative for non-severe outpatient community-acquired pneumonia. Adult dose 500 mg twice daily for 7 days. SEPAR 2024 first-line is high-dose amoxicillin, with a macrolide added for suspected atypical pathogens. Cefuroxime axetil is used in penicillin intolerance or confirmed resistance.
- BCiprofloxacinSecond line · Fluoroquinolone antibacterialsCiprofloxacin is not first-line for community-acquired pneumonia. It is used only when Pseudomonas aeruginosa is suspected – typically in patients with structural lung disease. For standard CAP, respiratory fluoroquinolones – levofloxacin or moxifloxacin – are preferred.
How to read tiers A–F
Evidence tiers belong to the drug-indication pair, not to the drug as a whole: the same substance can be A for one condition and F for another.
- AStrong evidence – first or second line in international guidelines
- BRecommended in selected cases
- CStudy data contradict each other
- DBenefit not proven, no documented harm
- FDocumented harm, or risk without benefit