What is the appropriate dosage of Amoxicillin for children?

Amoxicillin Dosing for Pediatric Patients

For children 3 months and older, prescribe amoxicillin 90 mg/kg/day divided into 2 doses (every 12 hours) for respiratory tract infections including pneumonia, with a maximum daily dose of 4000 mg. 1, 2, 3

Standard Dosing by Clinical Indication

Respiratory Tract Infections (Pneumonia, Bronchitis)

Mild to Moderate Infections:

• 45 mg/kg/day divided every 12 hours for children in areas with low pneumococcal resistance 1, 2, 4
• This provides adequate coverage while minimizing adverse effects 3
• Maximum daily dose: 4000 mg 2, 4

Severe Infections or High Pneumococcal Resistance Areas:

• 90 mg/kg/day divided every 12 hours (preferred regimen) 1, 2, 3, 5
• This higher dose is necessary to achieve adequate middle ear fluid and tissue penetration against resistant Streptococcus pneumoniae 6
• Each dose provides 45 mg/kg given twice daily 5

Group A Streptococcal Infections (Pharyngitis, Scarlet Fever)

• 50-75 mg/kg/day divided into 2 doses 2, 3, 5
• Duration: 10 days minimum to prevent acute rheumatic fever 3, 5, 4
• Maximum: 1000 mg per dose 2, 3
• Patients become non-contagious after 24 hours of therapy 3

Haemophilus influenzae Infections

• β-lactamase negative: 75-100 mg/kg/day divided into 3 doses 5
• β-lactamase producing: Switch to amoxicillin-clavulanate 45 mg/kg/day in 3 doses OR 90 mg/kg/day in 2 doses 2, 5

Age-Specific Dosing Considerations

Infants Under 3 Months (12 weeks)

• Maximum dose: 30 mg/kg/day divided every 12 hours due to incompletely developed renal function 4
• This lower dose accounts for reduced amoxicillin elimination in this age group 4

Children 3 Months and Older, Weight <40 kg

Mild/Moderate Infections:

• 25 mg/kg/day divided every 12 hours OR 20 mg/kg/day divided every 8 hours 4

Severe Infections:

• 45 mg/kg/day divided every 12 hours OR 40 mg/kg/day divided every 8 hours 4

Children ≥40 kg

Mild/Moderate Infections:

• 500 mg every 12 hours OR 250 mg every 8 hours 4

Severe Infections:

• 875 mg every 12 hours OR 500 mg every 8 hours 4

Renal Impairment Adjustments

GFR 10-30 mL/min:

• 500 mg or 250 mg every 12 hours (depending on infection severity) 4

GFR <10 mL/min:

• 500 mg or 250 mg every 24 hours 4

Hemodialysis:

• 500 mg or 250 mg every 24 hours, with additional dose during and at end of dialysis 4
• Do NOT use 875 mg dose in patients with GFR <30 mL/min 4

Treatment Duration

• Respiratory infections: 7-10 days 2, 3
• Pneumonia specifically: 10 days 2, 5
• Group A Streptococcal infections: 10 days minimum (mandatory to prevent rheumatic fever) 3, 5, 4
• Continue for minimum 48-72 hours beyond symptom resolution 4

Critical Prescribing Details

Every prescription must include: 3

• Total daily dose in mg/kg/day
• Number of divided doses per day
• Duration of therapy
• Indication for prescription
• Child's weight 7

Dosing Frequency: Why Twice Daily is Preferred

Twice-daily dosing (every 12 hours) is preferred over three-times-daily dosing because: 3

• Improves adherence and compliance 8, 9
• Provides similar efficacy to three-times-daily regimens 8, 9
• More convenient for families 8
• Research demonstrates comparable clinical cure rates between once/twice daily versus three times daily dosing 8

Monitoring and Follow-Up

Expected Clinical Response:

• Children should demonstrate clinical improvement within 48-72 hours of starting treatment 2, 3, 5
• If no improvement by 72 hours, reassess diagnosis and consider resistant organisms or alternative diagnoses 3, 5

Complete the full prescribed course even if symptoms improve before completion 2, 3

Common Adverse Effects

• Gastrointestinal disturbances (diarrhea, nausea, vomiting) are most common 2, 3
• Rash, urticaria, and hypersensitivity reactions may occur 2, 3
• Adverse event rates are comparable between twice-daily and three-times-daily dosing regimens 8

Critical Clinical Pitfalls

Inadequate Dosing in Viral Coinfection:

• Viral coinfection in acute otitis media reduces amoxicillin middle ear fluid penetration 6
• The conventional 40 mg/kg/day dose is inadequate to eradicate resistant S. pneumoniae, particularly during viral coinfection 6
• This supports the recommendation for 75-90 mg/kg/day dosing 6

Weight-Based Dosing in Obese Children:

• Prescribers often underdose older and heavier children 10
• When calculated dose exceeds standard adult dose (1500 mg/day), there is inconsistency in prescribing practices 10
• Use weight-based dosing up to maximum of 4000 mg/day 2, 4

MRSA Coverage:

• Amoxicillin alone will NOT be effective against MRSA 3
• If MRSA is suspected or confirmed, alternative antibiotics (vancomycin or clindamycin) must be added 1

Administration Instructions

• Take at the start of a meal to minimize gastrointestinal intolerance 4
• For oral suspension: shake well before each use 4
• After reconstitution, discard unused suspension after 14 days 4
• Refrigeration is preferable but not required 4