What is the recommended dosage of amoxicillin (amoxicillin) for an 11-year-old patient weighing 92 pounds with streptococcal pharyngitis (strep throat)?

Amoxicillin Dosing for Strep Throat in an 11-Year-Old Weighing 92 Pounds

For an 11-year-old child weighing 92 pounds (41.8 kg), give amoxicillin 1,000 mg once daily for 10 days, as this patient exceeds 40 kg and should receive the maximum adult dose. 1

Weight-Based Dosing Algorithm

For children weighing less than 40 kg:

• Use 50 mg/kg once daily (maximum 1,000 mg) for 10 days 1
• Alternative: 25 mg/kg twice daily (maximum 500 mg per dose) for 10 days 1

For children weighing 40 kg or more (including this patient at 41.8 kg):

• Give the adult dose of 1,000 mg once daily for 10 days 1
• Alternative: 500 mg twice daily for 10 days 1

Since this patient weighs 92 pounds (41.8 kg), the weight-based calculation of 50 mg/kg would yield 2,090 mg, but the maximum dose is capped at 1,000 mg once daily 1, 2. The FDA label confirms that patients weighing more than 40 kg should receive adult dosing regimens 2.

Critical Treatment Requirements

Complete the full 10-day course even if symptoms resolve earlier - this is essential to prevent acute rheumatic fever, which can occur if Group A Streptococcus is not adequately eradicated 3, 1. The American Heart Association emphasizes that therapy can be safely delayed up to 9 days after symptom onset and still prevent rheumatic fever, but once started, the full course must be completed 3.

Patients become non-contagious after 24 hours of antibiotic therapy 3, 1, allowing return to school or normal activities at that point.

Administration Instructions

• Give amoxicillin at the start of a meal to minimize gastrointestinal side effects 2
• Once-daily dosing may improve adherence compared to multiple daily doses 3, 1
• Amoxicillin suspension is considerably more palatable than penicillin V suspension if liquid formulation is needed 3

Evidence Supporting Once-Daily Dosing

The American Heart Association endorsed once-daily amoxicillin dosing based on comparative clinical trials showing equivalent efficacy to traditional penicillin V given 2-3 times daily 3. Research demonstrates that amoxicillin at 40-50 mg/kg/day achieves superior bacteriologic cure rates (79.3%) compared to conventional lower-dose penicillin V (54.5%) 4. The once-daily regimen carries a "Strong, high" recommendation based on quality evidence 1.

Common Pitfalls to Avoid

• Do not shorten the course below 10 days - even a few days' reduction significantly increases treatment failure rates and rheumatic fever risk 1
• Do not exceed 1,000 mg daily dose - higher doses provide no additional benefit and may increase side effects 1, 2
• Do not use amoxicillin/clavulanate (Augmentin) for initial treatment - this is reserved for treatment failures or chronic carriers 5

Alternative Options for Penicillin Allergy

If this patient had a penicillin allergy:

• Non-immediate allergy: Cephalexin 500 mg twice daily for 10 days 1, 6
• Immediate/anaphylactic allergy: Clindamycin 300 mg three times daily for 10 days or azithromycin 500 mg once daily for 5 days 1, 6