Recommended Dose of Cefalexin for a 38 kg Child
The recommended dose of cefalexin for a 38 kg child is 25-50 mg/kg/day divided into 4 doses (every 6 hours), which equals approximately 950-1900 mg total daily dose, divided into 4 doses of 237.5-475 mg every 6 hours. 1
Dosage Calculation Based on Weight
For a 38 kg child, the dosage calculation works out as follows:
- Standard dosage range: 25-50 mg/kg/day 1
- For a 38 kg child: 38 kg × 25-50 mg/kg = 950-1900 mg per day
- Divided into 4 doses (every 6 hours): 237.5-475 mg per dose
Alternative Dosing Schedules
According to the FDA label, cefalexin can be administered in different schedules depending on the type of infection:
- For streptococcal pharyngitis and skin/skin structure infections in children over 1 year of age, the total daily dose may be divided and administered every 12 hours 1
- For otitis media, clinical studies have shown that a higher dosage of 75-100 mg/kg/day in 4 divided doses is required 1
Dosage Based on Infection Type
The appropriate dosage may vary based on the specific infection being treated:
- For mild to moderate infections: 25-50 mg/kg/day divided into 4 doses 1
- For streptococcal pharyngitis: Total daily dose may be divided and administered every 12 hours 1
- For otitis media: 75-100 mg/kg/day in 4 divided doses 1
- For severe infections: The dosage may be doubled 1
Formulation Options
For a 38 kg child (approximately 84 lb), the FDA label provides the following guidance for suspension formulations:
- Using 250 mg/5 mL suspension:
- For q.i.d. (4 times daily) dosing: 1-2 teaspoons per dose
- For b.i.d. (twice daily) dosing: 2-4 teaspoons per dose 1
Recent Evidence on Alternative Dosing
Recent research suggests that less frequent dosing regimens may be effective and improve adherence:
A 2020 study found that for Staphylococcus aureus infections, a twice-daily (BID) dosing of 22-45 mg/kg or thrice-daily (TID) dosing of 15-25 mg/kg may be effective for organisms with MICs of 1-2 mg/L 2
A 2025 study demonstrated that high-dose cefalexin at 45 mg/kg (maximum 1.5 g) three times daily was effective and well-tolerated in children with bone and joint infections, with 99% of children achieving cure 3
Important Considerations
- For β-hemolytic streptococcal infections, cefalexin should be administered for at least 10 days 1
- If daily doses greater than 4 g are required, parenteral cephalosporins should be considered 1
- After mixing the suspension, it should be stored in the refrigerator and may be kept for 14 days without significant loss of potency 1
Conclusion
For a 38 kg child, the standard dose of cefalexin is 25-50 mg/kg/day divided into 4 doses, resulting in approximately 237.5-475 mg per dose given every 6 hours. The specific dosing regimen may be adjusted based on the type and severity of infection being treated.