What are the appropriate dosing regimens, treatment durations, and precautions for amoxicillin in pediatric patients with common bacterial infections such as acute otitis media, sinusitis, community‑acquired pneumonia, streptococcal pharyngitis, and skin infections?

Amoxicillin Dosing for Pediatric Bacterial Infections

First-Line Treatment Recommendations

For most pediatric bacterial infections, amoxicillin at 90 mg/kg/day divided into 2 doses (maximum 4 g/day) is the definitive first-line therapy, providing superior coverage against resistant Streptococcus pneumoniae and optimal clinical outcomes. 1, 2

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Community-Acquired Pneumonia

Outpatient Management (Children ≥3 months)

• Prescribe amoxicillin 90 mg/kg/day in 2 divided doses for all children with presumed bacterial pneumonia 3, 1, 4
• This high-dose regimen is essential to overcome pneumococcal resistance; underdosing with 40-45 mg/kg/day is a dangerous and common error 1, 4
• Treatment duration is 10 days for pneumonia 1, 2
• Children should show clinical improvement within 48-72 hours; if no improvement occurs, reevaluation and possible hospitalization are necessary 1, 2, 4

Special Populations

• For children <5 years who are not fully immunized against H. influenzae type b or with concurrent purulent otitis media: use amoxicillin-clavulanate 90 mg/kg/day of the amoxicillin component in 2 doses instead of amoxicillin alone 3, 1, 4
• For children ≥5 years with atypical features (gradual onset, prominent cough, minimal fever): add azithromycin 10 mg/kg on day 1, then 5 mg/kg/day on days 2-5 3, 1, 4

Inpatient Management

• Fully immunized, low-risk children: ampicillin 150-200 mg/kg/day IV every 6 hours OR penicillin G 100,000-250,000 U/kg/day IV every 4-6 hours 3, 4
• Alternative: ceftriaxone 50-100 mg/kg/day IV every 12-24 hours 3, 4
• Not fully immunized or high-risk: ceftriaxone 50-100 mg/kg/day OR cefotaxime 150 mg/kg/day every 8 hours 3, 4
• If MRSA suspected (severe presentation, necrotizing infiltrates, empyema, recent influenza): add vancomycin 40-60 mg/kg/day every 6-8 hours OR clindamycin 40 mg/kg/day every 6-8 hours 3, 4

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Acute Bacterial Sinusitis

Standard Dosing (Children ≥2 years, no risk factors)

• Amoxicillin 45 mg/kg/day in 2 divided doses for uncomplicated cases 3
• In communities with >10% nonsusceptible S. pneumoniae, initiate treatment at 80-90 mg/kg/day in 2 divided doses (maximum 2 g per dose) 3

High-Risk Patients

Use high-dose amoxicillin-clavulanate (80-90 mg/kg/day of amoxicillin component with 6.4 mg/kg/day clavulanate in 2 doses) for: 3

• Children <2 years old
• Children attending daycare
• Recent antibiotic use within past 30 days
• Moderate to severe illness at presentation

Treatment Duration

• Continue therapy for 7 days after the patient becomes symptom-free (minimum 10 days total) 3
• For children unable to tolerate oral medication: single dose ceftriaxone 50 mg/kg IV/IM, then switch to oral therapy if improved at 24 hours 3

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Group A Streptococcal Pharyngitis

Standard Regimen

• Amoxicillin 50-75 mg/kg/day in 2 doses for 10 days (maximum 1000 mg per dose) 3, 1
• Alternative once-daily dosing: 750 mg once daily improves adherence without compromising efficacy 1
• Patients become non-contagious after 24 hours of antibiotic therapy 1

Key Considerations

• Complete the full 10-day course regardless of symptom improvement to prevent acute rheumatic fever 1
• Fever and constitutional symptoms typically resolve within 3-4 days 1
• Antibiotic therapy may be started up to 9 days after symptom onset and still prevent acute rheumatic fever 1

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Acute Otitis Media

Standard Dosing

• High-dose amoxicillin 80-90 mg/kg/day in 2 divided doses is recommended for most children with AOM 5, 6, 7
• Standard-dose amoxicillin (40 mg/kg/day) is inadequate to eradicate resistant S. pneumoniae, particularly during viral coinfection 6

High-Risk Patients Requiring Amoxicillin-Clavulanate

• Children who received antibiotics within the past 4-6 weeks 3
• Severe illness at presentation 3
• Treatment failure on standard amoxicillin 3

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Skin and Soft Tissue Infections

Methicillin-Susceptible S. aureus (MSSA)

• Outpatient: oral cephalexin 75-100 mg/kg/day in 3-4 doses 3, 2
• Inpatient: cefazolin 150 mg/kg/day IV every 8 hours 3

Methicillin-Resistant S. aureus (MRSA)

• Outpatient: clindamycin 30-40 mg/kg/day in 3-4 doses (only if local resistance <10%) 3, 2
• Inpatient: vancomycin 40-60 mg/kg/day every 6-8 hours OR clindamycin 40 mg/kg/day every 6-8 hours 3

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Penicillin Allergy Management

Non-Severe Allergic Reactions (Non-Anaphylactic)

• Second- or third-generation cephalosporins are safe alternatives (cross-reactivity risk approximately 1-3%) 3, 4
• Options include: cefdinir, cefpodoxime, cefuroxime, or cephalexin 3, 4

Severe Allergic Reactions (Anaphylaxis, Type I Hypersensitivity)

• For pneumonia: levofloxacin 16-20 mg/kg/day in 2 doses (ages 6 months-5 years) OR 8-10 mg/kg once daily (ages 5-16 years; maximum 750 mg/day) 3, 4
• Alternative: linezolid 30 mg/kg/day in 3 doses (<12 years) OR 20 mg/kg/day in 2 doses (≥12 years) 3, 4
• For pharyngitis: clindamycin 20 mg/kg/day in 3 doses OR azithromycin 12 mg/kg once daily for 5 days 1

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Critical Dosing Considerations

Maximum Doses

• Maximum daily amoxicillin dose: 4000 mg (4 g) regardless of weight 1, 2
• Maximum single amoxicillin dose: 1000 mg for pharyngitis 1
• Maximum single dose for sinusitis/pneumonia: 2000 mg (2 g) 3

Common Pitfalls to Avoid

• Never underdose amoxicillin at 40-45 mg/kg/day for pneumonia when 90 mg/kg/day is indicated 1, 4
• Do not use macrolides as first-line therapy for presumed bacterial pneumonia in children <5 years 1, 4
• Do not use cefixime or cefdinir as first-line therapy for pediatric pneumonia 4
• Always consider MRSA in severe pneumonia with necrotizing infiltrates, empyema, or recent influenza 4
• Reassess all patients at 48-72 hours; lack of improvement requires reevaluation and possible treatment adjustment 1, 2, 4

Weight-Based Transitions

• Children weighing ≥40 kg should be dosed using standard adult regimens 1