Amoxicillin Dosing for 3-Year-Old with Ear Infection (38 lbs)
For this 3-year-old child weighing 38 pounds (17.3 kg) with acute otitis media, prescribe amoxicillin 80-90 mg/kg/day divided into two doses daily, which equals approximately 1400-1550 mg total daily dose, or 700-775 mg twice daily for 5 days. 1, 2
Weight-Based Calculation
- 38 pounds = 17.3 kg 2
- Total daily dose: 80-90 mg/kg/day = 1384-1557 mg/day 1, 2
- Divided into 2 doses: approximately 700-780 mg twice daily 1, 3
- Practical dosing: 750 mg twice daily (using available suspension concentrations) 3
Treatment Duration
- For children over 2 years of age: 5 days of treatment is appropriate 1
- Children under 2 years require 8-10 days of treatment, but this 3-year-old falls into the older age category 1
Why High-Dose Amoxicillin
High-dose amoxicillin (80-90 mg/kg/day) is recommended as first-line therapy because it achieves middle ear fluid levels that exceed the minimum inhibitory concentration for intermediately resistant and many highly resistant Streptococcus pneumoniae strains. 1, 4
- Standard-dose amoxicillin (40-45 mg/kg/day) is inadequate for resistant pneumococcal strains 5, 4
- High-dose achieves bacteriologic eradication in 92% of S. pneumoniae cases, including penicillin-nonsusceptible strains 4
- The dosing should be divided into two daily doses rather than three, as this improves compliance without compromising efficacy 1, 6
When to Consider Alternative Antibiotics
Switch to amoxicillin-clavulanate (90 mg/kg/day of amoxicillin component with 6.4 mg/kg/day clavulanate in 2 divided doses) if: 1, 2
- The child has taken amoxicillin within the past 30 days 1
- Concurrent purulent conjunctivitis is present (suggests H. influenzae) 1
- Treatment failure occurs after 48-72 hours 1
Monitoring for Treatment Failure
Reassess the child at 48-72 hours if symptoms persist or worsen. 1
Treatment failure is defined as: 1
- Worsening of the patient's condition
- Persistence of symptoms beyond 48 hours of antibiotic therapy
- Recurrence of symptoms within 4 days after treatment completion
Common Pitfalls to Avoid
- Do not use standard-dose amoxicillin (40 mg/kg/day) in areas with drug-resistant S. pneumoniae, which is now prevalent throughout the United States 1, 4
- Ensure adequate visualization of the tympanic membrane before prescribing antibiotics; isolated redness without other findings does not warrant treatment 1
- Administer amoxicillin at the start of meals to minimize gastrointestinal intolerance 3
- Do not prescribe antibiotics for otitis media with effusion unless it persists beyond 3 months 1
Practical Prescribing Instructions
Using amoxicillin oral suspension 250 mg/5 mL: 3
- Prescribe: 15 mL (750 mg) twice daily for 5 days
- Total volume needed: 150 mL bottle
- Shake well before each use
- Refrigeration is preferable but not required
- Discard unused portion after 14 days 3
Special Considerations for This Age Group
For children over 2 years of age, observation without immediate antibiotics is reasonable for non-severe cases, but this requires certain criteria: 1
- Absence of high fever (>38.5°C)
- Absence of intense earache
- Reliable follow-up within 48-72 hours 1
However, if the decision is made to treat with antibiotics (which is appropriate for most cases of confirmed AOM), high-dose amoxicillin remains first-line therapy. 1, 2