Cephalexin Liquid Dosing for Pediatric Bacterial Infections
For pediatric patients with bacterial infections, cephalexin liquid should be dosed at 25-50 mg/kg/day divided into 3-4 doses (every 6-8 hours), with higher doses of 75-100 mg/kg/day reserved for severe infections like otitis media. 1
Standard Dosing Regimens
Routine Infections
- Standard dose: 25-50 mg/kg/day divided every 6 hours (four times daily) 1
- Alternative dosing: For streptococcal pharyngitis and skin/soft tissue infections, the total daily dose may be divided and given every 12 hours (twice daily) 1
- This provides flexibility for adherence while maintaining efficacy
Severe Infections
- Otitis media: Requires 75-100 mg/kg/day in 4 divided doses 1
- Severe infections: The standard dosage may be doubled 1
- For β-hemolytic streptococcal infections, continue therapy for at least 10 days 1
Practical Weight-Based Dosing Tables
The FDA label provides specific guidance using the 125 mg/5 mL and 250 mg/5 mL suspensions 1:
Four Times Daily Dosing:
- 10 kg child: 1/2 to 1 teaspoon of 125 mg/5 mL suspension 1
- 20 kg child: 1 to 2 teaspoons of 125 mg/5 mL suspension 1
- 40 kg child: 2 to 4 teaspoons of 125 mg/5 mL suspension 1
Twice Daily Dosing (for pharyngitis/skin infections):
- 10 kg child: 1 to 2 teaspoons of 125 mg/5 mL suspension 1
- 20 kg child: 2 to 4 teaspoons of 125 mg/5 mL suspension 1
- 40 kg child: 4 to 8 teaspoons of 125 mg/5 mL suspension 1
Pathogen-Specific Considerations
Methicillin-Susceptible Staphylococcus aureus (MSSA)
- Preferred oral agent: Cephalexin 75-100 mg/kg/day in 3-4 doses for pneumonia or serious infections 2
- For skin and soft tissue infections: 25-50 mg/kg/day in 4 divided doses 2
- Recent evidence supports 45 mg/kg/dose (maximum 1.5 g) three times daily as an effective alternative with 99% cure rates in bone/joint infections 3
Group A Streptococcus
- Amoxicillin remains preferred (50-75 mg/kg/day in 2 doses) 2
- Cephalexin is an acceptable alternative for penicillin-allergic patients (except immediate hypersensitivity reactions) 2
Evidence-Based Alternative Dosing
Recent pharmacokinetic studies challenge traditional four-times-daily dosing:
- Three times daily: 22-45 mg/kg/dose achieves pharmacodynamic targets for MSSA with MIC 1-2 mg/L 4
- High-dose TID: 45 mg/kg/dose (maximum 1.5 g) three times daily demonstrated 99% efficacy in bone/joint infections with good tolerability 3
- Twice daily: Requires 22-45 mg/kg/dose for MSSA with MIC 1-2 mg/L, but 80 mg/kg/dose for MIC 4 mg/L 4
These reduced-frequency regimens improve adherence without compromising efficacy 4, 3.
Important Clinical Considerations
Preparation and Storage
- Reconstitute suspension at dispensing by adding specified water volume in two portions, shaking well after each 1
- Store reconstituted suspension refrigerated 1
- Discard after 14 days to prevent loss of potency 1
Pharmacokinetic Factors
- Children have greater body water turnover and may require higher per-kilogram doses than adults 5
- Cephalexin achieves urinary concentrations of 500-1000 mcg/mL following 250-500 mg doses, far exceeding MICs for urinary pathogens 5
- 70-100% of the dose appears in urine within 6-8 hours 5
Common Pitfalls to Avoid
- Do not use for MRSA infections - cephalexin has no activity against methicillin-resistant organisms 2
- Reduce dosage proportionally in patients with creatinine clearance <30 mL/min 5
- For serious infections requiring >4 g/day in adults, consider parenteral cephalosporins instead 1
- Ensure adequate duration: minimum 10 days for streptococcal infections 1