What is the recommended dose of cephalexin (cephalosporin) for treating uncomplicated cellulitis?

Cephalexin Dosing for Uncomplicated Cellulitis

For adults with uncomplicated cellulitis, cephalexin 500 mg four times daily (every 6 hours) orally for 5-7 days is the recommended dose. 1, 2

Adult Dosing Recommendations

• Standard dose: 500 mg orally four times daily (every 6 hours) 1, 2
• Alternative dosing: 500 mg every 12 hours is acceptable for skin and soft tissue infections, though four times daily is more commonly recommended 2
• Duration: 5 days is as effective as 10 days if clinical improvement occurs by day 5 1
• Severe infections: May require doses up to 4 grams daily in divided doses, though if >4 g/day is needed, consider parenteral cephalosporins 2

Pediatric Dosing

• Standard dose: 25-50 mg/kg/day divided into four doses 1, 2
• Alternative: For skin infections, the total daily dose may be divided every 12 hours 2
• Severe infections: Dosage may be doubled 2

Key Clinical Considerations

Cephalexin is appropriate first-line therapy because:

• β-hemolytic streptococci (particularly group A streptococcus) are the predominant pathogens in typical cellulitis 1, 3
• MRSA is an unusual cause of typical, non-purulent cellulitis 1, 3
• A large randomized trial demonstrated that adding trimethoprim-sulfamethoxazole (for MRSA coverage) to cephalexin provided no additional benefit for uncomplicated cellulitis 1, 4

When cephalexin may NOT be appropriate:

• Cellulitis associated with penetrating trauma, especially from illicit drug use 1
• Presence of purulent drainage or abscess 1
• Concurrent evidence of MRSA infection elsewhere 1, 3
• Rapid progression despite β-lactam therapy 1
• Severe systemic toxicity requiring hospitalization 1

Important Caveats

Avoid concurrent acid suppression therapy: One study found a 40% failure rate with cephalexin versus 20% with comparator antibiotics, potentially related to concurrent acid suppressive therapy reducing cephalexin absorption 5

Penicillin allergy: Cephalexin is appropriate for penicillin-allergic patients EXCEPT those with immediate hypersensitivity reactions (anaphylaxis, urticaria) 1

Adjunctive measures are essential:

• Elevate the affected area to promote drainage of edema 1, 3
• Treat predisposing conditions: tinea pedis, venous insufficiency, eczema 1, 3

Alternative First-Line Agents

If cephalexin is not suitable, other appropriate oral β-lactams include:

• Penicillin VK 250-500 mg every 6 hours 1
• Amoxicillin 500 mg three times daily 1
• Dicloxacillin 500 mg four times daily 1
• Clindamycin 300-450 mg four times daily (provides both streptococcal and MRSA coverage) 1