What is the first‑line antibiotic, dose, and duration for an otherwise healthy child with uncomplicated community‑acquired pneumonia, and what are the alternatives if the child has a penicillin allergy or is severely ill?

Antibiotic Treatment for Pediatric Community-Acquired Pneumonia

First-Line Therapy for Outpatient Management

Amoxicillin 90 mg/kg/day divided into 2 doses (maximum 4 g/day) for 5–7 days is the definitive first-line treatment for otherwise healthy children with uncomplicated community-acquired pneumonia. 1

Preschool Children (< 5 years)

• High-dose amoxicillin 90 mg/kg/day divided twice daily for 5–7 days is the standard empiric therapy for presumed bacterial pneumonia in fully immunized outpatients. 1
• If the child is not fully immunized against Haemophilus influenzae type b or Streptococcus pneumoniae, switch to amoxicillin-clavulanate with the amoxicillin component dosed at 90 mg/kg/day divided twice daily to cover β-lactamase-producing organisms. 1
• Azithromycin (10 mg/kg on day 1, then 5 mg/kg once daily on days 2–5) is reserved for the rare cases of presumed atypical pneumonia in this age group, as Mycoplasma pneumoniae is uncommon under age 5. 1

School-Age Children (≥ 5 years)

• Amoxicillin 90 mg/kg/day divided twice daily (maximum 4 g/day) for 5–7 days remains first-line for presumed bacterial pneumonia. 1
• When clinical features do not clearly differentiate bacterial from atypical pneumonia, add azithromycin (10 mg/kg day 1, then 5 mg/kg daily days 2–5; maximum 500 mg day 1,250 mg thereafter) to the amoxicillin regimen, as atypical pathogens (Mycoplasma pneumoniae, Chlamydophila pneumoniae) are significantly more common in school-age children. 1, 2
• For isolated atypical pneumonia with minimal bacterial features, azithromycin monotherapy using the same dosing is appropriate. 1

Inpatient Management

Low-Risk, Fully Immunized Children

• Ampicillin 150–200 mg/kg/day intravenously every 6 hours OR penicillin G 200,000–250,000 U/kg/day intravenously every 4–6 hours is the preferred empiric regimen for hospitalized children who are fully immunized and in areas with minimal penicillin resistance. 1, 3
• Ceftriaxone 50–100 mg/kg/day intravenously once daily (or every 12–24 hours) may be used as an alternative, though narrower-spectrum penicillins are preferred when appropriate. 1

Not Fully Immunized or High-Risk Children

• Ceftriaxone 50–100 mg/kg/day intravenously OR cefotaxime 150 mg/kg/day intravenously every 8 hours is recommended to cover penicillin-resistant S. pneumoniae and β-lactamase-producing H. influenzae in children who are incompletely immunized or in areas with significant local resistance. 1, 4

Suspected MRSA (Severe Pneumonia, Necrotizing Features, Empyema, Recent Influenza)

• Add vancomycin 40–60 mg/kg/day intravenously every 6–8 hours OR clindamycin 40 mg/kg/day intravenously every 6 hours to the β-lactam regimen when community-associated MRSA is suspected based on severe presentation, necrotizing pneumonia, empyema, or recent influenza infection. 1, 4
• Failure to consider MRSA coverage in these severe presentations is a critical and potentially life-threatening pitfall. 1

Hospitalized Atypical Pneumonia

• Azithromycin 10 mg/kg intravenously on days 1 and 2, then transition to oral therapy (5 mg/kg daily), is the preferred regimen for hospitalized children with atypical pneumonia. 1, 2
• Erythromycin lactobionate 20 mg/kg/day intravenously every 6 hours is an alternative if azithromycin is unavailable. 2

Penicillin Allergy Management

Non-Severe Allergic Reactions (Rash Without Anaphylaxis)

• Oral cephalosporins such as cefpodoxime, cefprozil, or cefuroxime can be used under medical supervision, as cross-reactivity risk between penicillins and cephalosporins is low (1–3%). 1, 4
• Azithromycin (10 mg/kg day 1, then 5 mg/kg daily days 2–5; maximum 500 mg/250 mg) is a safe β-lactam-free alternative that provides coverage for both typical and atypical pathogens. 1, 2

Severe Allergic Reactions (Anaphylaxis, Angioedema)

• Levofloxacin is the preferred alternative for severe penicillin allergy:
  • Children 6 months–5 years: 16–20 mg/kg/day divided twice daily
  • Children 5–16 years: 8–10 mg/kg once daily (maximum 750 mg/day) 1, 5
• Linezolid may be used as an alternative: 30 mg/kg/day divided three times daily for children < 12 years, or 20 mg/kg/day divided twice daily for children ≥ 12 years. 1, 5

Clinical Monitoring and Treatment Failure

• Children receiving appropriate therapy should demonstrate clinical improvement—reduced fever, improved respiratory effort, better oral intake—within 48–72 hours. 1, 2
• If no improvement or clinical deterioration occurs within 48–72 hours:
  • Obtain blood cultures and consider pleural-fluid sampling if an effusion is present. 1
  • Reassess for complications including parapneumonic effusion, empyema, necrotizing pneumonia, or lung abscess. 1
  • Consider resistant organisms (MRSA, penicillin-resistant S. pneumoniae) or alternative diagnoses. 1
  • Escalate to intravenous antibiotics if the patient is outpatient, or broaden coverage if already hospitalized. 1

Critical Pitfalls to Avoid

• Do not use macrolides as first-line monotherapy for presumed bacterial pneumonia in children < 5 years; they lack reliable activity against S. pneumoniae, the most common bacterial pathogen. 1, 2
• Do not underdose amoxicillin; the high dose of 90 mg/kg/day (not 40–45 mg/kg/day) is required to overcome pneumococcal resistance and is supported by pharmacokinetic data. 1, 2
• Do not use cefixime or cefdinir as first-line empiric therapy; they provide inadequate pneumococcal coverage compared with high-dose amoxicillin. 1
• Do not delay adding vancomycin or clindamycin in severe pneumonia with necrotizing features, empyema, or post-influenza presentation, as MRSA is a life-threatening possibility that requires immediate coverage. 1
• Do not continue inadequate therapy beyond 48–72 hours without reassessment; prompt escalation prevents treatment failure and reduces morbidity. 1, 2