What is the treatment for cellulitis of the left leg?

Treatment of Left Leg Cellulitis

For uncomplicated cellulitis of the left leg, initiate a 5-day course of oral antibiotics targeting streptococci—specifically cephalexin 500 mg four times daily, amoxicillin, dicloxacillin, or clindamycin 300-450 mg three times daily—and elevate the leg to promote drainage. 1, 2

Antibiotic Selection for Typical Cellulitis

The cornerstone of treatment is targeting streptococci, which cause the majority of non-purulent cellulitis cases. 1, 3, 4

First-line oral options include:

• Cephalexin 500 mg four times daily 2, 5
• Amoxicillin 2, 5
• Dicloxacillin 2, 5
• Penicillin 2, 5
• Clindamycin 300-450 mg three times daily (particularly useful for penicillin-allergic patients) 1, 2, 5

Critical point: MRSA is an unusual cause of typical cellulitis without purulent drainage, and routine MRSA coverage is unnecessary in uncomplicated cases. 1, 2 A prospective study demonstrated 96% success with beta-lactams alone (cefazolin or oxacillin), confirming that MRSA coverage is usually not needed. 1

When to Add MRSA Coverage

Add MRSA-active antibiotics only if specific risk factors are present: 1, 2

• Penetrating trauma (especially from injection drug use) 1, 2, 5
• Purulent drainage present 1, 2, 5
• Evidence of MRSA infection elsewhere on the body 1, 2, 5
• Known MRSA nasal colonization 1
• Systemic inflammatory response syndrome 1

MRSA treatment options when indicated:

• Oral: Trimethoprim-sulfamethoxazole, clindamycin alone, or doxycycline combined with a beta-lactam for streptococcal coverage 1, 2, 5
• IV (for severe cases): Vancomycin, daptomycin, linezolid, or telavancin 1, 2

Important caveat: A recent double-blind study showed that combining trimethoprim-sulfamethoxazole with cephalexin was no more effective than cephalexin alone for pure cellulitis without purulent drainage. 1

Duration of Therapy

Treat for 5-6 days initially. 1, 2, 5 This shorter course is as effective as 10-14 day regimens when clinical improvement occurs by day 5. 1, 5

Extend treatment beyond 5 days only if: 1, 2

• The infection has not improved within the initial 5-day period
• Erythema continues to expand
• Systemic symptoms persist

The evidence supporting shorter courses comes from multiple trials, including one comparing 5 versus 10 days of levofloxacin (no significant difference in outcomes), and two RCTs showing 6 days of tedizolid was equivalent to 10 days of linezolid. 1

Essential Adjunctive Measures

Elevation of the affected leg is critical to promote gravity drainage of edema and inflammatory substances, which hastens improvement. 1, 2, 5

Address predisposing factors immediately: 1, 2

• Examine and treat interdigital toe spaces for tinea pedis or maceration 1, 2, 5
• Manage venous insufficiency and lymphedema 1, 2, 5
• Treat any trauma or skin breakdown 1, 2
• Address obesity if present 2

Consider systemic corticosteroids (prednisone 40 mg daily for 7 days) in non-diabetic patients to reduce inflammation and potentially hasten resolution. 1, 5 A small pilot study showed that adding ibuprofen 400 mg every 6 hours for 5 days significantly shortened time to complete resolution (all patients resolved in 4-5 days versus up to 7+ days with antibiotics alone). 6

Hospitalization Criteria

Admit for IV antibiotics if any of the following are present: 2

• Systemic inflammatory response syndrome (fever, tachycardia, hypotension) 1, 2
• Altered mental status or hemodynamic instability 2
• Concern for deeper or necrotizing infection 2
• Severe immunocompromise 2
• Failure of outpatient treatment 2
• Poor adherence anticipated 2

Prevention of Recurrence

Cellulitis recurs in 8-20% of patients annually, typically in the same location. 1, 7

For patients with 3-4 episodes per year despite treating predisposing factors, initiate prophylactic antibiotics: 1, 2, 5

• Oral penicillin or erythromycin twice daily 1, 2, 5
• Intramuscular benzathine penicillin 1.2-2.4 million units every 2-4 weeks 1, 2, 5

Two randomized trials demonstrated substantial reduction in recurrences with twice-daily oral penicillin or erythromycin compared to controls. 1 Duration is indefinite, as infections may recur once prophylaxis stops. 1

Common Pitfalls to Avoid

Do not routinely cover MRSA in typical non-purulent cellulitis without specific risk factors—this leads to unnecessary broad-spectrum antibiotic use. 1, 2, 5 Two-thirds of hospitalized cellulitis patients receive overly broad-spectrum treatment without improved outcomes. 1

Do not extend antibiotics beyond 5 days if clinical improvement has occurred—this contributes to antibiotic overuse without added benefit. 1, 5

Do not overlook simple elevation of the affected leg, which is often as important as antibiotics for promoting resolution. 1, 5

Do not miss cellulitis mimickers such as venous stasis dermatitis, contact dermatitis, eczema, lymphedema, or deep vein thrombosis, which are frequently misdiagnosed as cellulitis. 8, 4

Do not forget to examine toe web spaces in lower extremity cellulitis—treating fissuring or fungal infection reduces recurrence risk. 1, 5