What is the recommended dose of Amoxicillin for a 5-year-old child weighing 34.8 pounds with pharyngeal streptococcal infection?

Amoxicillin Dosing for Pharyngeal Streptococcal Infection in a 5-Year-Old

For this 5-year-old child weighing 34.8 pounds (15.8 kg) with pharyngeal streptococcal infection, prescribe amoxicillin 710 mg twice daily (45 mg/kg/day divided into 2 doses) for 10 days. 1

Weight-Based Dosing Calculation

• Patient weight: 34.8 pounds = 15.8 kg
• Standard dosing: 45 mg/kg/day divided into 2 doses 1
• Calculated dose: 15.8 kg × 45 mg/kg/day = 711 mg/day, given as approximately 355 mg twice daily 1
• Practical dosing: Round to 350-400 mg twice daily using available suspension concentrations (typically 250 mg/5 mL or 400 mg/5 mL formulations) 2

Treatment Duration

• Minimum 10 days of treatment is mandatory to prevent acute rheumatic fever, regardless of symptom resolution 1, 2
• Treatment should continue for at least 10 days even if the child becomes asymptomatic after 3-4 days 1
• Therapy can be safely initiated up to 9 days after symptom onset and still prevent rheumatic fever 1

Why Amoxicillin is First-Line

• Amoxicillin is the antibiotic of choice for group A streptococcal pharyngitis due to its effectiveness, safety, acceptable taste (important for pediatric compliance), low cost, and narrow microbiologic spectrum 1
• Amoxicillin suspension is considerably more palatable than penicillin V suspension, improving adherence in children 1
• Group A streptococci have never developed resistance to penicillin or amoxicillin 1

Alternative Options for Penicillin Allergy

If non-anaphylactic penicillin allergy:

• First-generation cephalosporins (cephalexin or cefadroxil) for 10 days 1
• Risk of cross-reactivity between penicillins and first-generation cephalosporins is minimal (less than 10%) 1

If immediate Type I hypersensitivity (anaphylaxis) to beta-lactams:

• Erythromycin or other macrolides for 10 days 1
• These agents have limited effectiveness with bacterial failure rates of 20-25% 1

Critical Pitfalls to Avoid

• Never prescribe less than 10 days of treatment for streptococcal pharyngitis, as this is the only regimen proven to prevent acute rheumatic fever 1, 2
• Do not use azithromycin, clarithromycin, or TMP/SMX as first-line agents—these are reserved only for documented beta-lactam allergy 1
• Ensure the child takes medication at the start of meals to minimize gastrointestinal intolerance 2
• Counsel parents that the full 10-day course must be completed even when symptoms resolve after 3-4 days 1, 2

Administration Instructions

• Give amoxicillin at the start of a meal to minimize gastrointestinal side effects 2
• Shake oral suspension well before each use 2
• Refrigeration of reconstituted suspension is preferable but not required 2
• Discard any unused suspension after 14 days 2