What dose of medication should I use for a 50-kilogram child with streptococcal pharyngitis (strep throat)?

Antibiotic Treatment for a 50 kg Child with Strep Throat

For a 50 kg child with streptococcal pharyngitis, the recommended first-line treatment is amoxicillin 50 mg/kg once daily (maximum 1000 mg) or 25 mg/kg twice daily (maximum 500 mg per dose) for 10 days. 1

First-Line Treatment Options

Amoxicillin

• Dosing for a 50 kg child:
  • Option 1: 50 mg/kg once daily = 1000 mg (1 gram) once daily for 10 days
  • Option 2: 25 mg/kg twice daily = 500 mg twice daily for 10 days 1, 2
• Amoxicillin is often used in place of oral penicillin V for children due to better taste acceptance 3
• Should be taken at the start of a meal to minimize gastrointestinal intolerance 2

Penicillin V (Alternative First-Line)

• For a 50 kg child (adolescent dosing applies):
  • 250 mg three or four times daily for 10 days, OR
  • 500 mg twice daily for 10 days 3

Alternative Options for Penicillin-Allergic Patients

For Non-Anaphylactic Penicillin Allergy:

• First-generation cephalosporins for 10 days (varies by agent) 3, 1

For Severe/Anaphylactic Penicillin Allergy:

• Azithromycin: 12 mg/kg once daily (maximum 500 mg) for 5 days 1, 4
  • For a 50 kg child: 500 mg once daily for 5 days
• Clindamycin: 300-450 mg orally three times daily for 10 days 1

Important Treatment Considerations

Duration of Therapy

• A full 10-day course is recommended for penicillin, amoxicillin, and most other antibiotics (except azithromycin) 3, 1
• It is critical to complete the full course to:
  • Prevent acute rheumatic fever
  • Ensure bacterial eradication
  • Prevent transmission to close contacts 5

Treatment Monitoring

• Patients should show clinical improvement within 48-72 hours of starting antibiotics 1, 6
• If symptoms worsen or persist after 48-72 hours of antibiotic therapy, reevaluation is necessary 6
• Patients are considered non-contagious after 24 hours of effective antibiotic therapy 1

Common Pitfalls to Avoid

1. Underdosing: Using adult dosing for children under 40 kg can lead to treatment failure
2. Incomplete course: Not completing the full 10-day course increases risk of rheumatic fever 3, 5
3. Using macrolides as first-line: Resistance to azithromycin and clarithromycin exists in some regions 6
4. Unnecessary steroids: Corticosteroids are not routinely recommended for strep throat 6
5. Treating without confirmation: Treating based on clinical features alone without rapid antigen detection test or throat culture can lead to antibiotic overuse 7

Supportive Care

• Ibuprofen or acetaminophen for pain and fever relief
• Maintain adequate hydration
• Avoid aspirin in children due to risk of Reye syndrome 1

The 10-day course of amoxicillin at appropriate weight-based dosing remains the gold standard for treating strep throat in children, with excellent efficacy in preventing complications while maintaining good palatability and compliance.