What is the recommended dose of amoxicillin (amoxicillin) for streptococcal pharyngitis in children?

Pediatric Amoxicillin Dosing for Streptococcal Pharyngitis

For children with streptococcal pharyngitis, amoxicillin should be dosed at 50 mg/kg once daily (maximum 1,000 mg) or alternatively 25 mg/kg twice daily (maximum 500 mg per dose) for a full 10-day course. 1, 2

Standard Dosing Regimen

The once-daily dosing regimen (50 mg/kg, maximum 1,000 mg) is equally effective as twice-daily dosing and carries a "Strong, high" recommendation based on quality evidence. 1, 2 This recommendation comes from the Infectious Diseases Society of America (IDSA) 2012 guidelines, which represent the most authoritative source for this indication 1.

Weight-Based Dosing Details:

• Children weighing <40 kg: 50 mg/kg once daily (maximum 1,000 mg) OR 25 mg/kg twice daily (maximum 500 mg per dose) 1, 2
• Adolescents and adults (≥40 kg): 500 mg twice daily 1, 2
• Duration: Full 10 days required for all patients 1, 3

Why Once-Daily Dosing Works

Once-daily amoxicillin has been validated in multiple high-quality studies showing non-inferiority to twice-daily dosing 4. A 2006 randomized controlled trial of 652 children demonstrated bacteriologic failure rates of 20.1% for once-daily versus 15.5% for twice-daily at 14-21 days, with the difference falling within the prespecified non-inferiority margin 4. Real-time PCR studies confirm that once-daily dosing achieves equivalent bacterial eradication as multiple-daily dosing regimens 5.

The once-daily regimen may improve adherence without compromising efficacy, making it a practical first-line choice. 4

Critical Treatment Duration Requirement

A full 10-day course is absolutely essential to prevent acute rheumatic fever, regardless of symptom resolution. 1, 3 The FDA label explicitly states: "It is recommended that there be at least 10 days' treatment for any infection caused by Streptococcus pyogenes to prevent the occurrence of acute rheumatic fever" 3. Even though symptoms typically resolve within 3-4 days, shortening the course increases treatment failure rates and rheumatic fever risk 1.

Alternative Regimens for Penicillin Allergy

Non-Immediate (Non-Anaphylactic) Allergy:

• First-generation cephalosporins are preferred: Cephalexin 20 mg/kg twice daily (maximum 500 mg/dose) for 10 days 1, 6
• Cross-reactivity risk is only 0.1% in patients with non-severe, delayed penicillin reactions 6

Immediate/Anaphylactic Allergy:

• Clindamycin: 7 mg/kg three times daily (maximum 300 mg/dose) for 10 days - preferred due to ~1% resistance rate 1, 6
• Azithromycin: 12 mg/kg once daily (maximum 500 mg) for 5 days - acceptable but 5-8% macrolide resistance in US 1, 6
• Clarithromycin: 7.5 mg/kg twice daily (maximum 250 mg/dose) for 10 days 1

Avoid all cephalosporins in patients with immediate hypersensitivity reactions (anaphylaxis, angioedema, urticaria within 1 hour) due to up to 10% cross-reactivity risk. 1, 6

Common Pitfalls to Avoid

• Never prescribe shorter courses than 10 days (except azithromycin's 5-day regimen) - this increases treatment failure and rheumatic fever risk 1
• Do not use the 875 mg tablet formulation in children - dosing should be weight-based using suspension or appropriate tablet strengths 3
• Avoid prescribing antibiotics based on clinical features alone - confirm diagnosis with rapid antigen detection test or culture 1
• Do not perform routine post-treatment testing in asymptomatic patients who completed therapy 1

Administration Considerations

• Take at the start of meals to minimize gastrointestinal intolerance 3
• Shake oral suspension well before each use 3
• Reconstituted suspension remains stable for 14 days; refrigeration is preferable but not required 3
• Patients become non-contagious after 24 hours of antibiotic therapy 2

Adjunctive Therapy

• Ibuprofen or acetaminophen should be used for moderate to severe symptoms or high fever 1
• Never use aspirin in children due to Reye syndrome risk 1
• Corticosteroids are not recommended as adjunctive therapy 1

Special Populations

For infants <3 months (12 weeks): Maximum dose is 30 mg/kg/day divided every 12 hours due to incompletely developed renal function 3. However, streptococcal pharyngitis is uncommon in this age group and testing is generally not recommended unless risk factors are present 1.

For patients with severe renal impairment (GFR <30 mL/min): Dose adjustment required - do NOT use 875 mg formulation 3.