What is the recommended amoxicillin dosage for a 4‑year‑old child with uncomplicated acute otitis media who has no penicillin allergy and normal renal function?

Amoxicillin Dosing for a 4-Year-Old with Otitis Media

Prescribe high-dose amoxicillin at 80–90 mg/kg/day divided into two doses (given every 12 hours) for 10 days. 1, 2

Dose Calculation

• Calculate the total daily dose by multiplying the child's weight in kilograms by 90 mg/kg, then divide by 2 to determine each individual dose. 3, 4
• For example, a 4-year-old weighing 18 kg would receive: 90 mg/kg/day × 18 kg = 1,620 mg/day total, administered as 810 mg every 12 hours. 2
• Using the 400 mg/5 mL suspension, this equals approximately 10 mL twice daily. 4

Rationale for High-Dose Therapy

• High-dose amoxicillin achieves middle ear fluid concentrations that exceed the minimum inhibitory concentration for approximately 87% of Streptococcus pneumoniae isolates, including intermediately resistant strains (penicillin MIC 0.12–1.0 µg/mL). 1, 3
• This represents superior coverage compared to standard-dose amoxicillin (40–45 mg/kg/day), which covers only 83% of isolates. 1, 3
• The high-dose regimen maintains therapeutic levels throughout the dosing interval against the three principal AOM pathogens: S. pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. 3, 5

Treatment Duration

• Treat for 10 days in children younger than 6 years of age. 3, 4
• Continue treatment for a minimum of 48–72 hours beyond resolution of symptoms. 1, 6

When to Switch to Amoxicillin-Clavulanate

Switch to high-dose amoxicillin-clavulanate (90 mg/kg/day amoxicillin + 6.4 mg/kg/day clavulanate in a 14:1 ratio, divided twice daily) if any of the following apply: 1, 2, 3

• The child received amoxicillin within the previous 30 days 1, 3
• No clinical improvement or worsening after 48–72 hours of amoxicillin monotherapy 1, 4
• Concurrent purulent conjunctivitis (otitis-conjunctivitis syndrome) 2, 3
• Severe illness at presentation (high fever, marked otalgia) 3

The rationale for switching is that β-lactamase-producing H. influenzae (found in 58–82% of isolates) and M. catarrhalis are resistant to amoxicillin alone but susceptible to amoxicillin-clavulanate. 1, 2

Expected Clinical Response and Monitoring

• Clinical improvement (reduced pain, fever, irritability) should be evident within 48–72 hours of initiating therapy. 1, 3, 4
• Reassess the patient at 48–72 hours if symptoms fail to improve or worsen. 1, 4
• If the diagnosis of AOM is confirmed but the child has not improved on amoxicillin, switch to amoxicillin-clavulanate. 1, 3
• If the child fails amoxicillin-clavulanate, consider ceftriaxone 50 mg/kg IM or IV for three days. 3

Pain Management

• Address pain management during the first 24 hours regardless of antibiotic choice, using acetaminophen or ibuprofen as needed. 1, 4
• Pain management is a strong recommendation based on the preponderance of benefit over risk. 1

Common Pitfalls to Avoid

• Do not use standard-dose amoxicillin (40–45 mg/kg/day) as first-line therapy, as it provides inadequate coverage against intermediately resistant S. pneumoniae. 1, 2
• Verify the suspension concentration (125 mg/5 mL vs. 250 mg/5 mL vs. 400 mg/5 mL) before calculating the volume to dispense, as dosing errors are common. 2
• Do not exceed 4,000 mg/day total dose, even in larger children. 4
• Persistent middle ear effusion after treatment completion does not require additional antibiotics unless acute symptoms recur. 4
• The 14:1 ratio amoxicillin-clavulanate formulation (90/6.4 mg/kg/day) causes significantly less diarrhea than older 7:1 formulations while maintaining efficacy. 2, 3