Cephalexin Pediatric Dosing
Standard Dosing Recommendations
The FDA-approved pediatric dosage for cephalexin is 25-50 mg/kg/day divided into doses, with specific infections requiring higher doses up to 75-100 mg/kg/day. 1
Dosing by Indication
For most common infections (skin and soft tissue infections, uncomplicated UTIs): Use 25-50 mg/kg/day divided every 6 hours (four times daily) or every 12 hours (twice daily) 1
For methicillin-susceptible Staphylococcus aureus (MSSA) skin and soft tissue infections: Use the higher range of 75-100 mg/kg/day divided into 3-4 doses 2
For otitis media: Clinical studies demonstrate that 75-100 mg/kg/day in 4 divided doses is required for adequate treatment 1
For streptococcal pharyngitis and uncomplicated skin infections: The total daily dose may be divided and administered every 12 hours (twice daily) in patients over 1 year of age 1
Practical Dosing Examples by Weight
For standard infections (25-50 mg/kg/day) using suspension formulations 1:
- 10 kg child: 1/2 to 1 teaspoon of 125 mg/5 mL suspension four times daily, OR 1 to 2 teaspoons twice daily
- 20 kg child: 1 to 2 teaspoons of 125 mg/5 mL suspension four times daily, OR 2 to 4 teaspoons twice daily
- 40 kg child: 2 to 4 teaspoons of 125 mg/5 mL suspension four times daily, OR 4 to 8 teaspoons twice daily
Critical Dosing Considerations
For severe infections, the dosage may be doubled from the standard range 1
Avoid underdosing MSSA infections: Use the higher 75-100 mg/kg/day range rather than the standard 25-50 mg/kg/day to ensure adequate coverage 2
Cephalexin is NOT effective against MRSA and should only be used for methicillin-susceptible organisms 2
For β-hemolytic streptococcal infections: Administer therapeutic dosage for at least 10 days to prevent rheumatic fever 1
Alternative Dosing Frequencies
Recent pharmacokinetic studies support less frequent dosing to improve adherence 3, 4:
Three times daily dosing: 45 mg/kg/dose (maximum 1.5 g) three times daily has demonstrated efficacy and tolerability for bone and joint infections, achieving the same pharmacodynamic targets as four times daily dosing 3
Twice daily dosing: For MSSA with MIC 1-2 mg/L, doses of 22-45 mg/kg twice daily achieve adequate pharmacodynamic targets 4
Treatment Duration
Standard duration: Typically 7 days for most infections, depending on clinical response 2
Cystitis: Continue therapy for 7-14 days 1
Streptococcal infections: Minimum 10 days of treatment 1
Penicillin Allergy Considerations
Cephalexin is appropriate for penicillin-allergic patients EXCEPT those with immediate hypersensitivity (anaphylaxis) reactions 2
The cross-reactivity risk between penicillins and cephalosporins is low (approximately 1-3%) for non-anaphylactic reactions 5