What is the appropriate Augmentin (amoxicillin‑clavulanate) dose for a 4‑year‑old child weighing 37 lb with streptococcal pharyngitis, and what alternative therapy should be used if the child has a true penicillin allergy?

Augmentin Dosing for Streptococcal Pharyngitis in a 37-Pound Child

Direct Answer

Augmentin is NOT the first-line antibiotic for uncomplicated Group A streptococcal pharyngitis; use plain amoxicillin instead at 50 mg/kg once daily (maximum 1,000 mg) or 25 mg/kg twice daily (maximum 500 mg per dose) for 10 days. 1, 2

Why Amoxicillin Alone, Not Augmentin

• Plain amoxicillin is the preferred first-line treatment for Group A streptococcal pharyngitis in children, offering equivalent efficacy to penicillin V with better palatability and adherence. 1, 2
• Augmentin (amoxicillin/clavulanate) is reserved for treatment failures or chronic carriers who have not responded to initial therapy, not for routine first-line use. 3
• The addition of clavulanate provides no benefit against Group A Streptococcus, which does not produce β-lactamase, and only increases cost and gastrointestinal side effects. 1

Correct Amoxicillin Dosing for This Child

Weight conversion: 37 pounds = 16.8 kg

Two Equally Effective Regimens

Option 1 (Once-Daily):

• Dose: 50 mg/kg/day = 840 mg once daily (round to 750–800 mg based on available suspension concentrations)
• Maximum: 1,000 mg per dose
• Duration: 10 days 1, 2

Option 2 (Twice-Daily):

• Dose: 25 mg/kg per dose = 420 mg twice daily (round to 400–500 mg per dose)
• Maximum: 500 mg per dose
• Duration: 10 days 1, 2

Evidence Supporting Once-Daily Dosing

• Multiple randomized controlled trials demonstrate that once-daily amoxicillin (750 mg for children <40 kg) achieves bacteriologic eradication rates equivalent to multiple-daily dosing regimens. 4, 5, 6
• Once-daily dosing improves adherence without compromising efficacy, making it a practical choice for real-world practice. 1, 2

Critical Treatment Principles

• Complete the full 10-day course regardless of symptom improvement to prevent acute rheumatic fever; fever typically resolves within 3–4 days, but early discontinuation increases rheumatic fever risk. 1, 2
• Antibiotics may be started up to 9 days after symptom onset and still effectively prevent acute rheumatic fever. 1
• Never prescribe adult formulations (e.g., 875 mg tablets) for children under 40 kg, as this significantly exceeds recommended pediatric dosing. 2

When Augmentin IS Appropriate

If this child has already failed initial amoxicillin therapy or is a chronic carrier:

• Dose: 40 mg/kg/day of the amoxicillin component, divided into three doses
• Calculation: 16.8 kg × 40 mg/kg = 672 mg/day ÷ 3 = 224 mg per dose (round to 200–250 mg three times daily)
• Maximum: 2,000 mg/day of amoxicillin component
• Duration: 10 days 3

Penicillin Allergy Alternatives

Non-Anaphylactic Penicillin Allergy (e.g., rash without respiratory/cardiovascular symptoms)

• Cephalexin: 20 mg/kg per dose twice daily (maximum 500 mg per dose) for 10 days 1, 2
• Cefadroxil: 30 mg/kg once daily (maximum 1 g) for 10 days 1
• Cross-reactivity risk with cephalosporins is negligible in non-anaphylactic reactions. 1

True Type I (IgE-Mediated) Penicillin Allergy

• Clindamycin: 7 mg/kg per dose three times daily (maximum 300 mg per dose) for 10 days 1, 2
  • For this 16.8 kg child: 117 mg three times daily (round to 100–125 mg per dose)
• Azithromycin: 12 mg/kg once daily (maximum 500 mg) for 5 days 1, 2
  • Use cautiously due to potential macrolide resistance; check local resistance patterns before prescribing. 1

Common Pitfalls to Avoid

• Do not use Augmentin as first-line therapy for uncomplicated strep throat; it offers no advantage over plain amoxicillin and increases adverse effects. 3
• Do not prescribe shorter courses (e.g., 5 days) despite some studies suggesting efficacy; current guidelines do not endorse abbreviated therapy for routine use. 2
• Do not rely on clinical presentation alone; approximately 70% of sore throats in primary care are not streptococcal, so confirm with rapid antigen detection test or throat culture before prescribing antibiotics. 1
• Avoid sulfonamides and tetracyclines, which have high resistance rates and poor Group A Streptococcus eradication. 2

Alternative for Non-Adherent Patients

• Benzathine penicillin G: 600,000 units intramuscularly as a single dose (for children <27 kg) if oral adherence is unlikely 2
• This is the only regimen proven in controlled studies to prevent acute rheumatic fever. 2