Azithromycin Dosing for Strep Throat in a 1-Year-Old with Amoxicillin Allergy
For a 1-year-old child weighing 11.866 kg with strep throat and amoxicillin allergy, the appropriate dosage of azithromycin (Zithromax) is 10 mg/kg (118.7 mg) on day 1, followed by 5 mg/kg (59.3 mg) on days 2-5.
Dosage Calculation
For a child weighing 11.866 kg using Zithromax 600mg/15mL suspension:
- Day 1: 10 mg/kg × 11.866 kg = 118.7 mg
- Volume needed: (118.7 mg ÷ 600 mg) × 15 mL = 3 mL
- Days 2-5: 5 mg/kg × 11.866 kg = 59.3 mg
- Volume needed: (59.3 mg ÷ 600 mg) × 15 mL = 1.5 mL
Evidence-Based Rationale
The FDA-approved dosing for azithromycin in children for streptococcal pharyngitis follows a 5-day regimen 1:
- Day 1: 10 mg/kg (not to exceed 500 mg)
- Days 2-5: 5 mg/kg (not to exceed 250 mg)
This dosing regimen is supported by clinical studies showing effectiveness against Group A Streptococcus, with the higher initial dose providing rapid achievement of therapeutic levels 1.
Treatment Considerations for Strep Throat in Young Children
First-Line Treatment Options
- Amoxicillin is typically the first-line treatment for strep throat in children due to its effectiveness against Group A Streptococcus 2
- For patients with penicillin/amoxicillin allergy, macrolides such as azithromycin are the appropriate alternative 2
Effectiveness of Azithromycin
- Higher dosages of azithromycin (total course of 60 mg/kg) have been shown to be more effective than lower dosages (30 mg/kg) for streptococcal infections 3
- The 5-day regimen provides better bacterial eradication than shorter 3-day courses in children 3
Monitoring and Follow-Up
- Clinical improvement should be evident within 48-72 hours of starting therapy
- If no improvement occurs after 48-72 hours, reevaluation is necessary to consider complications or need for alternative therapy 2
Important Considerations
Advantages of Azithromycin
- Once-daily dosing improves compliance compared to multiple daily doses required with other antibiotics 4
- Shorter duration of treatment (5 days) compared to traditional 10-day courses for other antibiotics
Potential Concerns
- Gastrointestinal side effects (diarrhea, vomiting) are the most common adverse events with azithromycin 1
- Monitor for signs of allergic reaction, although cross-reactivity between penicillins and macrolides is rare
Administration Tips
- Azithromycin suspension can be given with or without food
- Shake well before each use
- Use a calibrated measuring device for accurate dosing
- Complete the full 5-day course even if symptoms improve before completion
By following this dosing regimen, you should achieve effective treatment of streptococcal pharyngitis in this young patient with amoxicillin allergy while minimizing the risk of treatment failure or complications.