Amoxicillin Dosing for Ear Infection in an 18-Pound Baby
For an 18-pound (approximately 8.2 kg) baby with acute otitis media, the recommended dose of amoxicillin is 80-90 mg/kg/day divided into two doses, which equals approximately 650-740 mg total daily dose. 1, 2
Dosing Calculation
- Weight: 18 pounds = 8.2 kg
- Recommended dose: 80-90 mg/kg/day in 2 divided doses
- Total daily dose: 656-738 mg/day
- Per dose (twice daily): 328-369 mg every 12 hours
Treatment Recommendations
First-Line Therapy
- High-dose amoxicillin is the first-line treatment for acute otitis media in children due to:
- Effectiveness against common pathogens
- Safety profile
- Low cost
- Acceptable taste
- Narrow microbiologic spectrum 1
Duration of Treatment
- For children under 2 years: 10-day course
- For children 2-5 years with mild/moderate symptoms: 7-day course
- For children ≥6 years with severe symptoms: 10-day course 2
Special Considerations
- If the child has taken amoxicillin in the previous 30 days, has concurrent conjunctivitis, or requires coverage for Moraxella catarrhalis, use amoxicillin-clavulanate instead (90 mg/kg/day of amoxicillin component with 6.4 mg/kg/day of clavulanate) 1
Treatment Failure Management
If symptoms worsen or fail to improve within 48-72 hours:
- Reassess diagnosis
- Consider switching to amoxicillin-clavulanate
- For severe cases or multiple treatment failures, consider referral to ENT specialist 2
Common Pitfalls and Caveats
Dosing Pitfalls
- Underdosing: Standard dose (40-45 mg/kg/day) may be inadequate for areas with high prevalence of resistant Streptococcus pneumoniae 3
- Weight calculation errors: Always convert pounds to kilograms accurately (1 kg = 2.2 pounds)
Important Clinical Considerations
- Always include pain management with acetaminophen or ibuprofen regardless of antibiotic choice 2
- Monitor for adverse effects, particularly diarrhea
- Ensure accurate diagnosis of AOM by confirming moderate to severe bulging of the tympanic membrane or new onset of otorrhea 2
- Be aware that 60-70% of children will still have middle ear effusion at 2 weeks after successful AOM treatment, which represents otitis media with effusion (OME), not treatment failure 2
Antibiotic Resistance Concerns
- Beta-lactamase-producing H. influenzae is the predominant pathogen in children failing high-dose amoxicillin therapy 4
- In areas with high prevalence of resistant S. pneumoniae, high-dose amoxicillin is particularly important 3
By following these evidence-based recommendations, you can effectively treat acute otitis media in this 18-pound baby while minimizing the risk of treatment failure and complications.