Amoxicillin Dosing for Strep Throat in Children of Different Weights
For children with strep throat, amoxicillin should be dosed at 50 mg/kg once daily (maximum 1000 mg) or alternatively 25 mg/kg twice daily (maximum 500 mg per dose) for 10 days. 1
Specific Dosing by Weight
Child weighing 25 kg:
- Once-daily dosing: 25 kg × 50 mg/kg = 1250 mg (use maximum of 1000 mg once daily) 1, 2
- Twice-daily dosing: 25 kg × 25 mg/kg = 625 mg (use 500 mg twice daily due to maximum dose limit) 1
Child weighing 40 kg:
- Once-daily dosing: 40 kg × 50 mg/kg = 2000 mg (use maximum of 1000 mg once daily) 1, 2
- Twice-daily dosing: 40 kg × 25 mg/kg = 1000 mg (use 500 mg twice daily due to maximum dose limit) 1
Child weighing 60 kg:
- Once-daily dosing: 60 kg × 50 mg/kg = 3000 mg (use maximum of 1000 mg once daily) 1, 2
- Twice-daily dosing: 60 kg × 25 mg/kg = 1500 mg (use 500 mg twice daily due to maximum dose limit) 1
Treatment Duration and Considerations
- A full 10-day course of therapy is essential to prevent acute rheumatic fever, even if symptoms resolve earlier 1, 2
- Amoxicillin is preferred over penicillin V for children due to better taste acceptance and similar efficacy 1
- Once-daily dosing has been shown to be non-inferior to twice-daily dosing, which may improve compliance 3
Alternative Regimens for Penicillin-Allergic Patients
For patients with penicillin allergy:
- Non-anaphylactic allergy: Cephalexin 20 mg/kg twice daily (max 500 mg/dose) for 10 days 1
- Anaphylactic allergy: Clindamycin 7 mg/kg three times daily (max 300 mg/dose) for 10 days 1
Important Clinical Considerations
- Despite some evidence supporting shorter treatment courses (5-7 days), the standard 10-day course remains recommended to prevent complications like acute rheumatic fever 4, 2
- Penicillin treatment failure rates have increased over time (now approximately 30%), making amoxicillin a good alternative 5
- Gastrointestinal side effects can be minimized by taking amoxicillin at the start of a meal 2
- Follow-up testing after treatment is not routinely recommended unless symptoms persist 1
Common Pitfalls to Avoid
- Underdosing: Using adult dosing for children may result in inadequate treatment 1
- Inadequate duration: Stopping antibiotics early when symptoms resolve increases risk of treatment failure and complications 2
- Inappropriate antibiotic selection: Using macrolides (azithromycin, clarithromycin) as first-line therapy is not recommended due to increasing resistance patterns 1, 6
- Failure to adjust for weight: Always calculate the dose based on the child's weight, up to the maximum recommended dose 1
Remember that amoxicillin is the preferred oral therapy for group A streptococcal pharyngitis in children due to its narrow spectrum, effectiveness, safety profile, and palatability 1.