What is the appropriate dose of cephalexin (cephalexin) for an 11-year-old boy?

Cephalexin Dosing for an 11-Year-Old Boy

The appropriate dose of cephalexin for an 11-year-old boy is 25 to 50 mg/kg/day divided into 2-4 doses, with a maximum of 4 grams per day. 1

Dosing Guidelines Based on FDA Label

The FDA-approved dosing for cephalexin in pediatric patients provides clear guidance:

• Standard recommended daily dosage: 25 to 50 mg/kg divided into multiple doses
• Dosing frequency options:
  • Four times daily (q.i.d.) - traditional dosing
  • Twice daily (b.i.d.) - for streptococcal pharyngitis and skin/skin structure infections
• For severe infections, the dosage may be doubled
• For otitis media, higher dosing of 75-100 mg/kg/day in 4 divided doses is required
• For β-hemolytic streptococcal infections, treatment should continue for at least 10 days 1

Practical Dosing Calculation

For an average 11-year-old boy (approximately 35-40 kg):

• Standard dose range: 875-2000 mg total daily dose
• Divided into 2-4 doses per day depending on infection type

Dosing Options:

1. Four times daily regimen:

   • 219-500 mg per dose (q.i.d.)

2. Twice daily regimen (for skin infections, streptococcal pharyngitis):

   • 438-1000 mg per dose (b.i.d.)

Recent Evidence on Less Frequent Dosing

Recent research supports less frequent dosing regimens to improve adherence while maintaining efficacy:

• A 2025 study demonstrated that three times daily dosing at 45 mg/kg/dose (maximum 1.5 g) was effective and well-tolerated for bone and joint infections 2
• A 2020 pharmacokinetic study found that twice-daily dosing at 22-45 mg/kg (for MSSA with MIC 1-2 mg/L) or 80 mg/kg (for MIC 4 mg/L) achieved adequate pharmacodynamic targets 3

Special Considerations

• Infection type matters: For more severe infections, use the higher end of the dosing range
• Duration of therapy: Typically 7-14 days, with a minimum of 10 days for streptococcal infections 1
• Formulation options: Available as suspension (125 mg/5 mL or 250 mg/5 mL) or capsules
• Renal function: Standard dosing is appropriate for children with normal renal function; dose adjustment is required for creatinine clearance <30 mL/min 4

Common Pitfalls to Avoid

• Underdosing: Inadequate dosing may lead to treatment failure and potential development of resistance
• Improper frequency: Using twice-daily dosing for infections that require more frequent administration
• Insufficient duration: Especially for streptococcal infections, which require a minimum of 10 days of therapy
• Poor adherence: Consider practical aspects of dosing frequency when prescribing; twice or three times daily regimens may improve compliance compared to four times daily dosing

Cephalexin is well-absorbed orally and provides good coverage against common pediatric pathogens, making it an excellent choice for many common infections in children when dosed appropriately.