What is the recommended dose of amoxicillin (amoxicillin) liquid for a 7-year-old boy weighing 33 kg with strep throat?

Amoxicillin Dosing for Strep Throat in a 7-Year-Old Child

For a 7-year-old boy weighing 33 kg with strep throat, the recommended dose of amoxicillin is 50 mg/kg/day once daily for 10 days, which equals 1,650 mg daily or approximately 20.6 mL of the 400 mg/5 mL suspension once daily. 1

Dosing Calculation

When using amoxicillin liquid 400 mg/5 mL for strep throat (Group A Streptococcal pharyngitis):

1. Weight-based calculation:

   • 33 kg × 50 mg/kg/day = 1,650 mg daily
   • Using 400 mg/5 mL suspension: 1,650 mg ÷ 400 mg × 5 mL = 20.6 mL daily

2. Alternative dosing option:

   • 25 mg/kg twice daily (maximum 500 mg per dose)
   • 33 kg × 25 mg/kg = 825 mg per dose (exceeds maximum, so use 500 mg)
   • 500 mg twice daily = 6.25 mL twice daily

Treatment Duration and Rationale

• Treatment must continue for a full 10 days to prevent acute rheumatic fever, even if symptoms resolve earlier 1, 2
• The 10-day duration is specifically recommended for Streptococcus pyogenes infections to prevent complications 2
• Treatment should continue for at least 48-72 hours beyond symptom resolution 2

Evidence Quality and Considerations

The IDSA guidelines (2012) provide strong, high-quality evidence supporting amoxicillin as first-line therapy for strep throat 1. The FDA label for amoxicillin confirms the need for 10 days of treatment for strep throat 2.

While some research has explored shorter treatment durations for other conditions 3, the 10-day course remains standard for strep throat to ensure complete eradication and prevent complications.

Administration Guidelines

• Administer amoxicillin at the start of a meal to minimize gastrointestinal intolerance 2
• Shake the oral suspension well before measuring each dose 2
• Use a calibrated measuring device for accurate dosing
• Store the reconstituted suspension in the refrigerator (preferred but not required) 2
• Discard any unused portion after 14 days 2

Monitoring and Follow-up

• Clinical improvement should be expected within 48-72 hours of starting treatment
• If no improvement is seen within this timeframe, reassessment is necessary
• No routine post-treatment testing is recommended for uncomplicated cases 1

Common Pitfalls to Avoid

1. Underdosing: Using standard-dose amoxicillin (40 mg/kg/day) may be inadequate for areas with resistant strains. The higher dose (50 mg/kg/day) is recommended by current guidelines 1, 4.

2. Insufficient duration: Stopping antibiotics early when symptoms resolve can lead to treatment failure and complications. Always complete the full 10-day course 1, 2.

3. Inaccurate measurement: Using household spoons instead of calibrated devices can lead to dosing errors.

4. Failure to recognize penicillin allergy: Always confirm absence of penicillin allergy before prescribing amoxicillin.

For penicillin-allergic patients, alternative treatments include cephalexin (if no immediate hypersensitivity), clindamycin, clarithromycin, or azithromycin, with appropriate weight-based dosing 1.