What is the recommended dose of amoxicillin (amoxicillin) for pediatric patients with varying ages, weights, and infection severity, considering potential allergies and impaired renal function?

Amoxicillin Dosing for Pediatric Patients

For most pediatric respiratory and common bacterial infections, use 45 mg/kg/day divided every 12 hours for mild-to-moderate infections, and 90 mg/kg/day divided every 12 hours for severe infections or areas with high pneumococcal resistance, with a maximum daily dose of 4000 mg. 1, 2

Standard Dosing Algorithm by Infection Severity

Mild to Moderate Infections

• For children ≥3 months and <40 kg: Administer 25 mg/kg/day divided every 12 hours (or 20 mg/kg/day divided every 8 hours) for ear/nose/throat, skin, and genitourinary infections 3
• For children ≥40 kg: Administer 500 mg every 12 hours or 250 mg every 8 hours 3
• The American Academy of Pediatrics specifically recommends 45 mg/kg/day divided every 12 hours as the preferred regimen for uncomplicated respiratory tract infections, providing adequate coverage while improving adherence with twice-daily dosing 1, 2

Severe Infections or High Pneumococcal Resistance

• For children ≥3 months and <40 kg: Administer 45 mg/kg/day divided every 12 hours (or 40 mg/kg/day divided every 8 hours) for lower respiratory tract infections 3
• High-dose regimen of 90 mg/kg/day divided every 12 hours is indicated for severe infections, areas with >10% penicillin-resistant S. pneumoniae, children <2 years old, recent antibiotic exposure within 30 days, or daycare attendance 1, 2
• For children ≥40 kg: Administer 875 mg every 12 hours or 500 mg every 8 hours 3

Age-Specific Considerations

Infants <3 Months (12 Weeks)

• Maximum dose is 30 mg/kg/day divided every 12 hours due to incompletely developed renal function affecting amoxicillin elimination 3
• Treatment should continue for at least 48-72 hours beyond symptom resolution 3
• There are currently no dosing recommendations for infants with impaired renal function in this age group 3

Children ≥3 Months

• Dosing is primarily weight-based rather than strictly age-based 2
• Twice-daily dosing (every 12 hours) improves adherence compared to three-times-daily regimens and is the preferred approach 1

Indication-Specific Dosing

Group A Streptococcal Infections (Strep Throat, Scarlet Fever)

• Dose: 50-75 mg/kg/day divided into 2 doses for 10 days, not exceeding 1000 mg per dose 1, 2
• The 10-day duration is mandatory to prevent rheumatic fever 1, 3
• Patients become non-contagious after 24 hours of therapy 1, 2

Community-Acquired Pneumonia

• Mild-to-moderate (outpatient): 45 mg/kg/day divided every 12 hours 1, 2
• Severe or high-resistance areas: 90 mg/kg/day divided every 12 hours 1, 2
• Treatment duration is 10 days 1, 2

Acute Otitis Media

• Standard dose: 45 mg/kg/day divided every 12 hours 2
• High-dose: 90 mg/kg/day divided every 12 hours for risk factors including age <2 years, recent antibiotic use, daycare attendance, or incomplete H. influenzae type b vaccination 2, 4

Renal Impairment Adjustments

• GFR 10-30 mL/min: 500 mg or 250 mg every 12 hours, depending on infection severity 1, 3
• GFR <10 mL/min: 500 mg or 250 mg every 24 hours 1, 3
• Hemodialysis: 500 mg or 250 mg every 24 hours, with an additional dose during and at the end of dialysis 3
• Patients with GFR <30 mL/min should NOT receive the 875 mg dose 3

Treatment Duration

• Most respiratory infections: 7-10 days 1, 2
• Pneumonia: 10 days specifically 1, 2
• Group A Streptococcal infections: 10 days mandatory 1, 3
• Continue treatment for a minimum of 48-72 hours beyond symptom resolution or evidence of bacterial eradication 3

Critical Administration Details

Prescription Requirements

• Every prescription should include: total daily dose in mg/kg/day, number of divided doses per day, duration of therapy, indication for prescription, and the child's weight 1
• Amoxicillin should be taken at the start of a meal to minimize gastrointestinal intolerance 3

Monitoring and Follow-Up

• Clinical improvement should occur within 48-72 hours of starting treatment 1, 2
• If no improvement by 72 hours, reassess the diagnosis and consider alternative antibiotics 1, 2
• Complete the full prescribed course even if symptoms improve 1, 2

Common Pitfalls to Avoid

Underdosing in Larger Children

• A significant clinical problem exists where larger children (>60 kg) frequently receive declining doses in mg/kg/day, often less than 40 mg/kg/day when high-dose therapy is indicated 5
• Children are reaching adult maximum doses at inappropriately low weights (around 20 kg), resulting in subtherapeutic dosing for older/heavier children 5
• Always calculate the dose based on actual weight in mg/kg/day first, then compare to the maximum daily dose of 4000 mg 1

Resistance Considerations

• If MRSA is suspected or confirmed, amoxicillin alone will not be effective and alternative antibiotics must be considered 1
• For β-lactamase-producing organisms (H. influenzae, M. catarrhalis), amoxicillin-clavulanate (Augmentin) should be used instead of amoxicillin alone 2, 4

Dosing Frequency

• Twice-daily dosing has equivalent efficacy to three-times-daily dosing but significantly improves adherence 1, 6
• The 45-90 mg/kg/day divided every 12 hours is the preferred approach over more frequent dosing schedules 1

Adverse Effects

• Most common: Gastrointestinal disturbances including diarrhea, nausea, and vomiting 1, 2
• Other reactions: Rash, urticaria, and hypersensitivity reactions 1, 2
• High-dose amoxicillin does not result in a greater incidence of adverse effects compared to standard doses 7, 8
• Monitor patients throughout treatment for these effects 1