What is the recommended dosing of cephalexin (cephalexin) for a pediatric patient with cellulitis, considering factors such as age, weight, and renal function (Impaired renal function)?

Cephalexin Dosing for Pediatric Cellulitis

For pediatric patients with cellulitis, cephalexin should be dosed at 25-50 mg/kg/day divided into 3-4 doses (every 6-8 hours), with the option to use twice-daily dosing (every 12 hours) for uncomplicated cases. 1, 2

Standard Dosing Regimen

For Non-Purulent Cellulitis (Streptococcal Coverage)

• Dose: 25-50 mg/kg/day divided into 3-4 doses (every 6-8 hours) 1, 2
• Alternative: For skin and soft tissue infections, the total daily dose may be divided and administered every 12 hours 2
• Duration: 5-10 days, individualized based on clinical response 1
• Maximum daily dose: Should not exceed 4 grams per day 2

Practical Dosing Examples

For a 20 kg child:

• Standard regimen: 500-1000 mg/day divided into 4 doses = 125-250 mg every 6 hours 2
• Simplified regimen: 500-1000 mg/day divided into 2 doses = 250-500 mg every 12 hours 2

Dosing Adjustments for Renal Impairment

Critical consideration: Cephalexin is renally eliminated and requires dose adjustment in patients with impaired renal function to prevent seizures and nephrotoxicity 3. Doses and dosing intervals must be reduced based on creatinine clearance 3.

Clinical Context and Treatment Selection

When Cephalexin is Appropriate

• Non-purulent cellulitis where β-hemolytic streptococci are the primary concern 1
• Regions where community-acquired MRSA prevalence is low (<10%) 4
• Patients without systemic toxicity or signs of MRSA infection 1

When Cephalexin is NOT Appropriate

• First-generation cephalosporins like cephalexin are ineffective for Lyme disease and should not be used when erythema migrans cannot be distinguished from cellulitis 1
• Purulent cellulitis (cellulitis with purulent drainage or exudate) requires empirical MRSA coverage with clindamycin, TMP-SMX, or other MRSA-active agents 1
• Patients with systemic inflammatory response syndrome (fever >38°C, tachycardia, tachypnea) may require broader coverage 1

Important Clinical Pearls

Efficacy Data

• Cephalexin demonstrates 91-92% cure rates for uncomplicated cellulitis when MRSA is not prevalent 5
• Treatment failure rates with oral cephalexin are approximately 8.9% in appropriate cases 5
• Oral therapy requires fewer ED visits (1.4 vs 3.4) and less time (164 vs 521 minutes) compared to IV therapy 5

Safety Monitoring

• Always use actual body weight in kilograms for dose calculations and document weight on every prescription 3
• Monitor for treatment failure at 48-72 hours; lack of improvement suggests MRSA or need for alternative therapy 1
• If patient fails β-lactam therapy, empirical MRSA coverage should be added 1

Common Pitfalls to Avoid

• Do not use cephalexin for MRSA coverage: It has no activity against methicillin-resistant organisms 1
• Do not underdose: Severe infections may require doubling the standard dose to 75-100 mg/kg/day 2
• Do not forget renal adjustment: Failure to adjust for renal impairment significantly increases toxicity risk 3
• Do not use for facial cellulitis near the eye: Periorbital/orbital cellulitis requires broader coverage with IV antibiotics like ceftriaxone 6

Alternative Considerations

If broader coverage is needed for hospitalized patients with complicated cellulitis:

• Cefazolin: 50 mg/kg/day IV divided every 8 hours for MSSA coverage 1
• Clindamycin: 25-40 mg/kg/day IV divided every 6-8 hours if MRSA suspected and local resistance <10% 1