What volume in milliliters of amoxicillin suspension should be given to a 5‑year‑old female with acute otitis media?

Amoxicillin Dosing for a 5-Year-Old with Acute Otitis Media

Prescribe high-dose amoxicillin at 80–90 mg/kg/day divided into two doses, and calculate the exact milliliter volume based on the child's weight and the concentration of your suspension (typically 400 mg/5 mL). 1, 2

Step-by-Step Calculation Algorithm

1. Obtain the Child's Weight

• Weigh the child in kilograms (a typical 5-year-old weighs approximately 18–20 kg). 1

2. Calculate Total Daily Dose

• Multiply the child's weight by 80–90 mg/kg to determine the total daily amoxicillin dose. 1, 2
• Example: For a 20 kg child: 20 kg × 80 mg/kg = 1,600 mg/day (minimum) or 20 kg × 90 mg/kg = 1,800 mg/day (maximum). 1

3. Divide Into Two Equal Doses

• Split the total daily dose in half to give every 12 hours. 1, 2
• Example: 1,600 mg ÷ 2 = 800 mg per dose, or 1,800 mg ÷ 2 = 900 mg per dose. 1

4. Convert Milligrams to Milliliters Based on Suspension Concentration

• Standard 400 mg/5 mL suspension: Divide the per-dose milligrams by 400, then multiply by 5 to get milliliters. 1
  • 800 mg ÷ 400 × 5 = 10 mL per dose
  • 900 mg ÷ 400 × 5 = 11.25 mL per dose
• Alternative 200 mg/5 mL suspension: Divide the per-dose milligrams by 200, then multiply by 5. 1
  • 800 mg ÷ 200 × 5 = 20 mL per dose

5. Specify Treatment Duration

• For mild-to-moderate symptoms: Prescribe a 7-day course. 2, 3
• For severe symptoms (moderate-to-severe otalgia, otalgia ≥48 hours, or fever ≥39°C): Prescribe a 10-day course. 1, 3

When to Switch to Amoxicillin-Clavulanate Instead

Use amoxicillin-clavulanate (90 mg/kg/day amoxicillin component + 6.4 mg/kg/day clavulanate, divided BID) as first-line therapy if any of the following apply: 1, 2, 3

• The child received amoxicillin within the past 30 days. 1, 2
• Concurrent purulent conjunctivitis is present (suggests Haemophilus influenzae). 1, 2
• The child attends daycare or lives in an area with high prevalence of β-lactamase-producing organisms. 1, 4

The 14:1 amoxicillin-to-clavulanate ratio formulation causes significantly less diarrhea than older 7:1 formulations while maintaining efficacy. 1

Reassessment Protocol

• Reassess at 48–72 hours if symptoms worsen or fail to improve. 1, 2, 3
• If amoxicillin fails, switch to amoxicillin-clavulanate at the high-dose regimen. 1, 2
• If amoxicillin-clavulanate fails, administer intramuscular ceftriaxone 50 mg/kg once daily for 3 consecutive days (superior to single-dose regimen). 1, 2

Pain Management (Critical First Step)

• Initiate weight-based acetaminophen or ibuprofen immediately for all children with ear pain, regardless of antibiotic decision. 2, 3
• Analgesics provide relief within 24 hours, whereas antibiotics provide no symptomatic benefit in the first 24 hours. 3
• Continue pain medication throughout the acute phase. 2, 3

Common Pitfalls to Avoid

• Do not use standard-dose amoxicillin (40–45 mg/kg/day): It achieves inadequate middle ear fluid concentrations against penicillin-resistant Streptococcus pneumoniae, particularly during viral coinfection. 5
• Do not prescribe azithromycin or other macrolides as first-line therapy: Pneumococcal macrolide resistance exceeds 40% in the United States, with bacterial failure rates of 20–25%. 1
• Do not use trimethoprim-sulfamethoxazole or erythromycin-sulfisoxazole for treatment failures: Resistance to these agents is substantial. 2
• Do not treat isolated tympanic membrane redness without middle ear effusion: This does not constitute acute otitis media and does not require antibiotics. 3

Pharmacodynamic Rationale

High-dose amoxicillin achieves middle ear fluid concentrations that exceed the minimum inhibitory concentration for approximately 87% of S. pneumoniae isolates (including intermediately resistant strains), compared with only 83% coverage using standard dosing. 1 Research demonstrates that after a 25 mg/kg oral dose, mean middle ear fluid concentrations reach approximately 9.5 µg/mL at 3 hours post-dose, with lower penetration during viral coinfection. 5 High-dose amoxicillin-clavulanate achieves 96% eradication of S. pneumoniae by days 4–6, significantly superior to azithromycin. 1, 6