What is the recommended oral treatment and duration for simple cellulitis?

Oral Treatment for Simple Cellulitis and Duration

For simple cellulitis, a 5-day course of oral antibiotics active against streptococci, such as cephalexin, dicloxacillin, or amoxicillin, is recommended as first-line therapy. 1

First-Line Antibiotic Selection

Recommended Oral Antibiotics:

• Cephalexin: 500 mg four times daily (standard dose) 1
• Dicloxacillin: 500 mg four times daily 1
• Amoxicillin: 500 mg three times daily 1
• Clindamycin: 300-450 mg three times daily (for penicillin-allergic patients) 1

Duration of Therapy:

• 5 days is the recommended duration for uncomplicated cellulitis 1, 2
• Treatment should be extended if the infection has not improved within this time period 1

Special Considerations

When to Consider MRSA Coverage:

Add coverage for MRSA only in specific circumstances:

• Penetrating trauma, especially from illicit drug use
• Evidence of MRSA infection elsewhere
• Nasal colonization with MRSA
• Injection drug use
• Purulent drainage
• Systemic inflammatory response syndrome (SIRS)
• Prior MRSA exposure
• High-risk populations (athletes, prisoners, military recruits, residents of long-term care facilities) 1, 3

MRSA Coverage Options:

• Clindamycin: 300-450 mg three times daily (covers both streptococci and MRSA)
• Trimethoprim-sulfamethoxazole (TMP-SMX) plus a beta-lactam (TMP-SMX alone has unreliable activity against streptococci)
• Doxycycline plus a beta-lactam 1

Treatment Algorithm

1. Assess severity:

   • Mild (no systemic signs): Oral antibiotics active against streptococci
   • Moderate (systemic signs): Consider hospitalization or close outpatient follow-up
   • Severe (failed oral therapy, immunocompromised, deeper infection signs): Hospitalize for IV antibiotics

2. Select antibiotic:

   • Standard case: Cephalexin 500 mg four times daily for 5 days
   • Penicillin allergy: Clindamycin 300-450 mg three times daily for 5 days
   • MRSA risk factors present: Add appropriate MRSA coverage

3. Adjunctive measures:

   • Elevate affected area to promote drainage of edema 1
   • Address predisposing factors (edema, venous insufficiency, tinea pedis) 1
   • In lower extremity cellulitis, examine interdigital toe spaces and treat any fissuring or maceration 1

4. Follow-up:

   • Extend treatment if no improvement after 5 days 1
   • Consider systemic corticosteroids (prednisone 40 mg daily for 7 days) in non-diabetic adults to hasten resolution 1, 4

Important Clinical Pearls

• Blood cultures and skin biopsies are not routinely recommended for typical cases of cellulitis 1
• MRSA is an unusual cause of typical cellulitis without purulence; a study showed 96% success with beta-lactam therapy alone 1
• Recent research suggests high-dose cephalexin (1000 mg four times daily) may reduce treatment failure compared to standard dose (500 mg four times daily), though with slightly more minor adverse effects 5
• A randomized controlled trial demonstrated that 5 days of levofloxacin was as effective as 10 days in patients who showed clinical improvement within the first 5 days 2

Common Pitfalls to Avoid

1. Overtreatment with MRSA coverage when not indicated - beta-lactam monotherapy is sufficient for most cases of simple cellulitis 1
2. Prolonged treatment courses beyond 5 days when not necessary - multiple studies show 5 days is sufficient for uncomplicated cases 1, 2
3. Failure to address predisposing factors - treating underlying conditions like tinea pedis, edema, or venous insufficiency is crucial to prevent recurrence 1
4. Missing deeper infection - watch for signs of necrotizing infection (bullae, skin sloughing, hypotension, or organ dysfunction) that require immediate surgical consultation 1