What is the recommended dosage of amoxicillin (amox) for pediatric patients with sinusitis in mg/kg/day?

Amoxicillin Dosing for Pediatric Sinusitis

For pediatric patients with acute bacterial sinusitis, the recommended amoxicillin dosage is 45 mg/kg/day divided into two doses (BID), or 90 mg/kg/day divided into two doses for high-dose therapy when antibiotic resistance is suspected or the child is at high risk. 1, 2

Standard vs High-Dose Regimens

Standard-Dose Amoxicillin

• 45 mg/kg/day divided BID is appropriate for uncomplicated acute bacterial sinusitis in children without risk factors for resistant organisms 1
• This dosing provides adequate coverage for susceptible Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis 3

High-Dose Amoxicillin

• 90 mg/kg/day divided BID (maximum 1 gram every 12 hours) is recommended when penicillin-resistant S. pneumoniae is suspected 1, 2
• This higher dose overcomes resistance mediated by altered penicillin-binding proteins in approximately 25-50% of S. pneumoniae strains 1
• The increased dose achieves sinus fluid concentrations adequate to eradicate resistant organisms 2

Risk Factors Requiring High-Dose Therapy

High-dose amoxicillin (90 mg/kg/day) should be used for children with: 2

• Age younger than 2 years (higher risk for harboring resistant organisms)
• Recent antibiotic exposure within the previous 30 days
• Severe infection at presentation
• Daycare attendance or other risk factors for resistant pathogens

Amoxicillin-Clavulanate (Augmentin) Considerations

When β-lactamase-producing organisms are suspected:

• Amoxicillin-clavulanate 80-90 mg/kg/day (based on amoxicillin component) with 6.4 mg/kg/day clavulanate in 2 divided doses 1, 2
• This formulation provides coverage against β-lactamase-producing H. influenzae and M. catarrhalis, which represent nearly 50% and 90-100% of isolates respectively in most geographic areas 1
• The clavulanate component is essential for β-lactamase-producing pathogens 2

Treatment Duration and Monitoring

• 10-14 days is the standard treatment duration 2, 3
• Some guidelines recommend continuing until 7 days after symptom resolution 2
• Reassess at 3-5 days: if no clinical improvement, consider changing antibiotics or reevaluating the diagnosis 2

Alternative Dosing from Older Guidelines

An older guideline from 2005 listed amoxicillin at 45 mg/kg BID for pediatric sinusitis 1, but this has been superseded by more recent recommendations emphasizing 90 mg/kg/day for high-risk patients 2, 3. The evolution reflects increasing antibiotic resistance patterns.

Important Caveats

• First-generation cephalosporins, macrolides, and trimethoprim-sulfamethoxazole are no longer recommended due to high resistance rates 1
• For children unable to tolerate oral medication, ceftriaxone 50 mg/kg IV/IM can be given as a single dose, with transition to oral therapy if improvement occurs at 24 hours 2
• One placebo-controlled trial found no benefit of amoxicillin 40 mg/kg/day over placebo 4, but this used suboptimal dosing by current standards and highlights the importance of adequate dosing for resistant organisms