What is the recommended dosage of cephalexin (antibiotic) for pediatric patients?

Pediatric Cephalexin Dosing Recommendations

The recommended dosage of cephalexin for pediatric patients is 25 to 50 mg/kg/day divided into 4 doses (given every 6 hours) for most infections, with specific conditions requiring higher doses. 1

Standard Dosing Guidelines

• General infections: 25-50 mg/kg/day divided into 4 doses (q.i.d.)
• Streptococcal pharyngitis (patients >1 year): Total daily dose may be divided and administered every 12 hours (b.i.d.)
• Skin and skin structure infections: Total daily dose may be divided and administered every 12 hours (b.i.d.)
• Otitis media: 75-100 mg/kg/day in 4 divided doses 1
• β-hemolytic streptococcal infections: Treatment should continue for at least 10 days 1

Weight-Based Dosing Chart

For 125 mg/5 mL suspension:

• 10 kg (22 lb): 1/2 to 1 tsp q.i.d. or 1 to 2 tsp b.i.d.
• 20 kg (44 lb): 1 to 2 tsp q.i.d. or 2 to 4 tsp b.i.d.
• 40 kg (88 lb): 2 to 4 tsp q.i.d. or 4 to 8 tsp b.i.d.

For 250 mg/5 mL suspension:

• 10 kg (22 lb): 1/4 to 1/2 tsp q.i.d. or 1/2 to 1 tsp b.i.d.
• 20 kg (44 lb): 1/2 to 1 tsp q.i.d. or 1 to 2 tsp b.i.d.
• 40 kg (88 lb): 1 to 2 tsp q.i.d. or 2 to 4 tsp b.i.d. 1

Special Considerations

Severe Infections

• For severe infections, the standard dosage may be doubled 1
• For bone and joint infections, recent evidence supports using 45 mg/kg/dose (maximum 1.5 g) three times daily 2

Alternative Dosing Schedules

While the FDA-approved dosing is four times daily, recent pharmacokinetic studies have explored less frequent dosing to improve adherence:

• Three times daily (TID) dosing: 15-25 mg/kg/dose for MSSA with MICs of 1-2 mg/L, and 45 mg/kg/dose for MICs of 4 mg/L 3
• Twice daily (BID) dosing: 22-45 mg/kg/dose for MSSA with MICs of 1-2 mg/L, and 80 mg/kg/dose for MICs of 4 mg/L 3

Renal Impairment

• Patients with creatinine clearances less than 30 ml/min require a reduction in cephalexin dosage proportional to the reduced renal function 4

Clinical Pearls

• Children may need higher doses per kilogram than adults due to their greater body water turnover 4
• For β-hemolytic streptococcal infections, treatment should continue for at least 10 days to prevent rheumatic fever 1
• After reconstitution, cephalexin suspension should be stored in the refrigerator and may be kept for 14 days without significant loss of potency 1
• Common errors to avoid include inadequate dosing of cephalexin and failure to reassess after 48-72 hours if no clinical improvement is observed 5

Emerging Evidence

Recent research suggests that less frequent dosing regimens may be effective while improving adherence:

• A 2024 study found that for musculoskeletal infections, cephalexin 25 mg/kg/dose (maximum 750 mg/dose) three times daily achieved pharmacodynamic targets for efficacy against MSSA 6
• A 2025 study demonstrated that high-dose cephalexin (45 mg/kg/dose, maximum 1.5 g) three times daily was effective and well-tolerated in children with bone and joint infections, with 99% achieving cure 2

While these alternative dosing schedules show promise, the FDA-approved dosing remains 25-50 mg/kg/day divided into 4 doses for most infections, with higher doses (75-100 mg/kg/day) for otitis media 1.