Amoxicillin 90 mg/kg Dosing Example
For a child requiring high-dose amoxicillin at 90 mg/kg per day, administer the total daily dose divided into 2 doses given every 12 hours. This dosing strategy is recommended for acute otitis media, acute bacterial sinusitis, and community-acquired pneumonia when coverage against resistant Streptococcus pneumoniae is needed 1.
Practical Dosing Example
For a 10 kg child:
- Total daily dose: 90 mg/kg/day × 10 kg = 900 mg per day
- Individual dose: 900 mg ÷ 2 = 450 mg every 12 hours
For a 20 kg child:
- Total daily dose: 90 mg/kg/day × 20 kg = 1800 mg per day
- Individual dose: 1800 mg ÷ 2 = 900 mg every 12 hours
Clinical Context and Indications
The 90 mg/kg/day dosing (maximum 4 g/day in adults) is specifically indicated for 1:
- Acute otitis media in children who have received amoxicillin in the previous 30 days
- Acute otitis media with concurrent purulent conjunctivitis
- Acute bacterial sinusitis in children <2 years, those attending daycare, or recently treated with antibiotics 2
- Community-acquired pneumonia when bacterial etiology (particularly pneumococcal) is suspected 3
When to Use High-Dose vs. Standard-Dose
High-dose amoxicillin (80-90 mg/kg/day) is warranted when 1, 2:
- Local penicillin-nonsusceptible S. pneumoniae prevalence exceeds 10%
- Child is <2 years old
- Recent antibiotic exposure (within 30 days)
- Daycare attendance
- Moderate to severe illness presentation
Standard-dose amoxicillin (45 mg/kg/day) is appropriate for 1:
- Children ≥2 years without recent antibiotic exposure
- Mild to moderate illness
- No daycare attendance
- Areas with low resistance rates
Amoxicillin-Clavulanate Formulation
When using high-dose amoxicillin-clavulanate (for β-lactamase producing organisms), the dosing is 1, 4:
- 90 mg/kg/day of amoxicillin component with 6.4 mg/kg/day of clavulanate
- Given in 2 divided doses (every 12 hours)
- Uses a 14:1 ratio formulation to minimize clavulanate-related diarrhea
- Maximum adult dose: 4000 mg amoxicillin per day
Duration of Therapy
- Acute otitis media: 5-7 days for children <2 years; 5 days for children ≥2 years 1
- Acute bacterial sinusitis: 10-14 days 2
- Community-acquired pneumonia: 5-10 days depending on clinical response 3
Important Caveats
Renal impairment: Do NOT use the 875 mg tablet formulation in patients with GFR <30 mL/min. Adjust frequency to every 12-24 hours based on severity of renal dysfunction 5.
Administration: Give at the start of meals to minimize gastrointestinal intolerance 5.
Suspension preparation: After reconstitution, shake well before each use. Discard unused suspension after 14 days. Refrigeration is preferable but not required 5.
The evidence strongly supports that high-dose amoxicillin achieves adequate sinus and middle ear fluid concentrations to overcome intermediate-level penicillin resistance in S. pneumoniae through pharmacokinetic/pharmacodynamic optimization 1, 4. Research demonstrates that 90 mg/kg/day dosing is safe and well-tolerated in children, with linear absorption allowing higher doses without significantly increased adverse effects 4.