Maximum Dose of Keflex (Cephalexin) in Pediatric Patients
The maximum daily dose of cephalexin in pediatric patients is 100 mg/kg/day, typically divided into 3-4 doses, with severe infections requiring doses at the upper end of this range. 1
Standard Dosing Framework
Routine Infections
- Standard pediatric dosing is 25-50 mg/kg/day divided into 4 doses for most common infections including uncomplicated skin and soft tissue infections 1
- For streptococcal pharyngitis and uncomplicated skin infections in patients over 1 year of age, the total daily dose may be divided and administered every 12 hours 1
Severe Infections and MSSA
- For methicillin-susceptible Staphylococcus aureus (MSSA) skin and soft tissue infections, use 75-100 mg/kg/day divided into 3-4 doses 2
- The FDA label explicitly states: "In severe infections, the dosage may be doubled" from the standard 25-50 mg/kg/day range 1
- For otitis media specifically, clinical studies have demonstrated that 75-100 mg/kg/day in 4 divided doses is required 1
Absolute Maximum Limits
Daily Dose Ceiling
- The maximum total daily dose is 4 grams per day, regardless of weight 1
- If daily doses greater than 4 grams are required, parenteral cephalosporins should be considered instead 1
Per-Dose Maximum
- Recent evidence supports high-dose cephalexin at 45 mg/kg/dose (maximum 1.5 grams per dose) administered three times daily for bone and joint infections, which has demonstrated efficacy and tolerability 3
- This translates to a maximum single dose of 1.5 grams 3
Practical Dosing by Weight
For a 40 kg (88 lb) child with severe infection:
- Standard severe infection dosing: 75-100 mg/kg/day = 3,000-4,000 mg/day total
- Divided four times daily: 750-1,000 mg per dose
- Divided three times daily: 1,000-1,333 mg per dose (not exceeding 1,500 mg/dose) 3
Critical Clinical Considerations
Common Pitfall to Avoid
- Do not underdose MSSA infections - use the higher 75-100 mg/kg/day range rather than the standard 25-50 mg/kg/day for these infections 2
- Cephalexin is only effective against methicillin-susceptible organisms and should never be used for MRSA 2
Allergy Considerations
- Cephalexin is appropriate for penicillin-allergic patients except those with immediate (Type 1) hypersensitivity reactions 4, 2
Duration of Therapy
- For β-hemolytic streptococcal infections, administer therapeutic dosage for at least 10 days 1
- Standard duration for most infections is typically 7 days, depending on clinical response 2
Tolerability of High Doses
- The high-dose regimen of 45 mg/kg three times daily (maximum 1.5 g/dose) is well tolerated in most children, with only 4/149 children experiencing gastrointestinal symptoms and 13 developing mild neutropenia without complications in one large study 3