Cefalexin Dosing for Pediatric Patients
Standard Dosing Recommendations
For most pediatric infections in children over 1 month of age, cefalexin should be dosed at 25-100 mg/kg/day divided into 2-4 doses depending on infection severity, with typical dosing being 25-50 mg/kg/day for mild infections and up to 100 mg/kg/day for severe infections. 1
Dosing by Infection Severity and Frequency
For mild to moderate infections: Administer 25-50 mg/kg/day divided into 3-4 doses (approximately 6-12 mg/kg per dose every 6-8 hours) 2
For severe infections or bone and joint infections: Use high-dose cefalexin at 45 mg/kg/dose (maximum 1.5 g per dose) three times daily, which has been shown to be effective and well-tolerated in 99% of pediatric patients 3
Alternative twice-daily dosing: For MSSA infections with MIC ≤2 mg/L, doses of 22-45 mg/kg twice daily achieve adequate pharmacodynamic targets, improving adherence by reducing dosing frequency 4
Pathogen-Specific Considerations
For methicillin-susceptible Staphylococcus aureus (MSSA) infections: The required dose depends on the organism's minimum inhibitory concentration:
For skin and soft tissue infections: Standard dosing of 10 mg/kg four times daily (40 mg/kg/day total) has demonstrated 97.4% microbiological eradication rates 2
Weight-Based Dosing Examples
- For a 9 kg child with mild infection: 75 mg every 8 hours 5
- For a 9 kg child with moderate infection: 150 mg every 8 hours 5
- For a 22.7 kg child with mild infection: 190 mg every 8 hours 5
- For a 22.7 kg child with moderate infection: 375 mg every 8 hours 5
Renal Impairment Adjustments
While specific pediatric renal dosing adjustments for cefalexin are not detailed in the provided guidelines, dose reduction and interval extension are necessary in patients with impaired renal function, as cefalexin is primarily renally eliminated. Standard practice requires monitoring renal function and adjusting doses accordingly, though specific pediatric protocols should be consulted for creatinine clearance-based adjustments.
Safety and Tolerability
Gastrointestinal effects: Approximately 4-8% of children experience diarrhea with cefalexin therapy 3, 2
Hematologic effects: Mild neutropenia may develop in approximately 9% of children on prolonged therapy, though this is typically mild and without clinical complications 3
Overall tolerability: The high-dose three times daily regimen (45 mg/kg/dose) is well-tolerated in most children, with only 2.7% experiencing gastrointestinal symptoms requiring attention 3
Critical Clinical Considerations
A common pitfall is using outdated four times daily dosing when three times daily high-dose regimens (45 mg/kg/dose) provide equivalent efficacy with improved adherence. 3 This is particularly important for bone and joint infections requiring prolonged oral therapy.
Never exceed adult maximum doses when calculating pediatric doses for larger children, as adult dose caps should be applied 5
For serious infections requiring broader coverage (such as those caused by β-lactamase-producing organisms), cefalexin is inadequate and alternative agents like amoxicillin-clavulanate or cefazolin should be used instead 6, 5