What is the recommended management for cellulitis in an inpatient setting?

Management of Cellulitis in the Inpatient Setting

For hospitalized adults with complicated cellulitis, vancomycin 15-20 mg/kg IV every 8-12 hours is the first-line agent, with treatment duration of 5 days if clinical improvement occurs, extending only if symptoms have not improved. 1

Initial Assessment and Risk Stratification

When a patient requires hospitalization for cellulitis, immediately assess for:

• Signs of systemic toxicity (fever, hypotension, tachycardia, confusion, altered mental status) 2, 1
• Rapid progression suggesting necrotizing fasciitis 1
• Purulent drainage or exudate indicating possible MRSA involvement 2, 1
• Predisposing factors such as penetrating trauma, injection drug use, or concurrent MRSA infection 2, 1

Blood cultures should be obtained in hospitalized patients, particularly those with malignancy, severe systemic features, neutropenia, or severe immunodeficiency 2. Tissue aspirates or skin biopsies should be considered in these high-risk populations 2.

Antibiotic Selection Algorithm

For Uncomplicated Cellulitis Requiring Hospitalization

Beta-lactam monotherapy remains appropriate even in the inpatient setting if the cellulitis is non-purulent and lacks MRSA risk factors. 2, 1

• IV cefazolin or oxacillin are effective in 96% of hospitalized cellulitis cases 2
• MRSA is an uncommon cause of typical cellulitis, even in hospitals with high MRSA prevalence 2
• Do not add MRSA coverage reflexively simply because the patient is hospitalized 2, 1

For Complicated Cellulitis with MRSA Risk Factors

First-line options for MRSA coverage: 1

• Vancomycin 15-20 mg/kg IV every 8-12 hours (preferred, A-I evidence)
• Linezolid 600 mg IV twice daily (alternative, A-I evidence)
• Daptomycin 4 mg/kg IV once daily (alternative, A-I evidence) 3
• Telavancin 10 mg/kg IV once daily (alternative, A-I evidence)
• Clindamycin 600 mg IV three times daily (alternative if local resistance rates are low, A-III evidence)

For Severe Cellulitis with Systemic Toxicity or Suspected Necrotizing Fasciitis

Mandatory broad-spectrum combination therapy is required: 1

• Vancomycin or linezolid PLUS one of the following:
  • Piperacillin-tazobactam 3.375-4.5 grams IV every 6 hours 1
  • A carbapenem (meropenem or imipenem)
  • Ceftriaxone plus metronidazole

For documented Group A streptococcal necrotizing fasciitis specifically: Penicillin plus clindamycin is the recommended combination 1

Treatment Duration

The standard duration is 5 days if clinical improvement has occurred, with extension only if the infection has not improved within this timeframe. 2, 1

• For complicated skin and soft tissue infections requiring hospitalization, 7-14 days may be necessary, guided by clinical response 1
• For necrotizing fasciitis or infections requiring surgical debridement, continue treatment for 7-14 days 1
• Reassess at day 5 to determine if extension is needed 1

Common Pitfalls to Avoid

Do not use piperacillin-tazobactam or other broad-spectrum agents for typical cellulitis. This represents significant overtreatment and should be reserved only for severe infections with systemic toxicity or suspected polymicrobial/necrotizing infections 1. Piperacillin-tazobactam lacks MRSA coverage and must always be combined with vancomycin or linezolid when used 1.

Do not combine daptomycin with piperacillin-tazobactam for simple cellulitis. This combination should be reserved only for life-threatening infections or documented resistant organisms 1. If you are using this combination, you are treating something more severe than typical cellulitis and should plan for 7-14 days minimum 1.

Do not reflexively add MRSA coverage in all hospitalized patients. Even in hospitals with high MRSA prevalence, beta-lactam monotherapy succeeds in 96% of typical cellulitis cases 2. MRSA coverage is indicated only for purulent cellulitis, penetrating trauma (especially injection drug use), or documented MRSA infection elsewhere 2, 1.

Adjunctive Measures

Elevation of the affected extremity hastens improvement by promoting gravity drainage of edema and inflammatory substances 2, 1

Treat predisposing conditions including:

• Tinea pedis and toe web abnormalities 2, 1
• Venous insufficiency and lymphedema 2, 1
• Trauma sites and surgical wounds 1

Systemic corticosteroids (prednisone 40 mg daily for 7 days) could be considered in non-diabetic adults, though evidence is limited (weak recommendation, moderate evidence) 2

Transition to Oral Therapy

Patients can transition to oral antibiotics once clinical improvement is demonstrated, typically after a minimum of 4 days of IV treatment 3. Suitable oral options include:

• Cephalexin 500 mg four times daily 1, 4
• Dicloxacillin 500 mg four times daily 2
• Clindamycin 300-450 mg four times daily (covers both streptococci and MRSA) 2, 1

For patients requiring continued MRSA coverage orally: Use clindamycin alone, or combine doxycycline or trimethoprim-sulfamethoxazole with a beta-lactam 2, 1. Never use doxycycline or trimethoprim-sulfamethoxazole as monotherapy for typical cellulitis, as their activity against beta-hemolytic streptococci is unreliable 2, 1.

Pediatric Considerations

For hospitalized children with complicated cellulitis: 1

• Vancomycin 15 mg/kg IV every 6 hours is first-line
• Clindamycin 10-13 mg/kg/dose IV every 6-8 hours is an option if local resistance rates are low
• Linezolid dosed at 600 mg IV twice daily for children >12 years, or 10 mg/kg/dose IV every 8 hours for children <12 years

Home IV therapy with ceftriaxone is non-inferior to hospital-based IV flucloxacillin for children with moderate to severe cellulitis and should be considered when feasible 5.