What is the appropriate amoxicillin dose for a 15.6 kg child using a suspension concentration of 250 mg per 5 mL?

Amoxicillin Dosing for 15.6 kg Child

For a 15.6 kg child, prescribe amoxicillin 700 mg twice daily (45 mg/kg/day divided into 2 doses), which equals 14 mL of the 250 mg/5 mL suspension twice daily.

Dosing Calculation

The appropriate dose depends on the clinical indication:

For Most Common Infections (Otitis Media, Sinusitis, Pharyngitis)

• Standard dosing: 45 mg/kg/day divided into 2 doses 1, 2
• Calculation: 15.6 kg × 45 mg/kg/day = 702 mg/day
• Practical dose: 700 mg/day = 350 mg twice daily
• Volume: 7 mL of 250 mg/5 mL suspension twice daily

For High-Risk Situations or Resistant Organisms

Use high-dose amoxicillin (80-90 mg/kg/day) if the child has:

• Attended daycare recently
• Received antibiotics within the past 30 days
• Age under 2 years
• Lives in an area with >10% penicillin-resistant S. pneumoniae 3

High-dose calculation:

• 15.6 kg × 90 mg/kg/day = 1,404 mg/day
• Practical dose: 1,400 mg/day = 700 mg twice daily
• Volume: 14 mL of 250 mg/5 mL suspension twice daily 1, 2

For Pneumonia

For community-acquired pneumonia with suspected S. pneumoniae:

• Preferred dose: 90 mg/kg/day in 2 doses 1, 2
• Calculation: 15.6 kg × 90 mg/kg/day = 1,404 mg/day
• Volume: 14 mL twice daily of 250 mg/5 mL suspension

For Group A Streptococcal Pharyngitis

• Dose: 50 mg/kg once daily (maximum 1000 mg) for 10 days 4
• Calculation: 15.6 kg × 50 mg/kg = 780 mg once daily
• Volume: 15.5 mL once daily of 250 mg/5 mL suspension

Alternatively, 25 mg/kg twice daily:

• 15.6 kg × 25 mg/kg = 390 mg twice daily
• Volume: 7.8 mL (round to 8 mL) twice daily

Practical Dispensing Instructions

Using the 250 mg/5 mL concentration 5:

For standard dosing (45 mg/kg/day):

• Give 7 mL twice daily

For high-dose therapy (90 mg/kg/day):

• Give 14 mL twice daily

Important Clinical Considerations

When to Use High-Dose Amoxicillin

The shift to high-dose amoxicillin addresses increasing pneumococcal resistance. You must use 80-90 mg/kg/day for:

• Acute otitis media in high-risk children
• Community-acquired pneumonia
• Acute bacterial sinusitis in children with recent antibiotic exposure 1, 3

Duration of Therapy

• Streptococcal pharyngitis: 10 days (mandatory to prevent rheumatic fever) 4, 5
• Pneumonia: Minimum 48-72 hours beyond symptom resolution 5
• Otitis media/sinusitis: Typically 10 days for children under 2 years; 5-7 days may suffice for older children with uncomplicated cases

Common Pitfalls to Avoid

1. Underdosing larger children: Research shows clinicians often prescribe declining mg/kg doses as children get heavier, leading to subtherapeutic levels in older/larger children 6

2. Not adjusting for resistance patterns: Standard-dose amoxicillin (40-45 mg/kg/day) is inadequate against intermediate-resistant S. pneumoniae, particularly during viral coinfection 7

3. Incorrect twice-daily conversion: When converting from three-times-daily to twice-daily dosing, ensure the total daily dose remains appropriate. The 25 mg/kg twice daily regimen provides better compliance than 15 mg/kg three times daily 8

4. Forgetting the maximum dose: While this 15.6 kg child is well below adult dosing limits, be aware that the maximum single dose is 2000 mg 5

Reconstitution and Storage

• Shake bottle until powder flows freely
• Add water per manufacturer instructions (see bottle label)
• Shake vigorously before each use
• Refrigeration preferred but not required
• Discard after 14 days 5

When Amoxicillin is Inappropriate

Do not use amoxicillin if:

• History of serious hypersensitivity to β-lactams (anaphylaxis, Stevens-Johnson syndrome) 5
• Suspected atypical pathogens (Mycoplasma, Chlamydia) require macrolide addition 1
• Suspected MRSA requires vancomycin or clindamycin 1