What antibiotic is used to treat cellulitis in an inpatient setting?

Antibiotic Treatment for Inpatient Cellulitis

Primary Recommendation

For hospitalized patients with complicated cellulitis, IV vancomycin is the first-line empirical therapy pending culture data, dosed at standard intervals, with treatment duration of 7-14 days based on clinical response. 1

Treatment Algorithm by Clinical Presentation

Nonpurulent Cellulitis (No Abscess, No Purulent Drainage)

Beta-lactam monotherapy is appropriate for most hospitalized patients with nonpurulent cellulitis, as MRSA is an uncommon cause and beta-lactam treatment succeeds in 96% of cases. 2

• IV cefazolin is the preferred beta-lactam agent for hospitalized patients with typical nonpurulent cellulitis 1
• Modify to MRSA-active therapy only if no clinical response occurs after 48-72 hours 1
• This approach avoids unnecessary broad-spectrum coverage in the majority of cases 2

Complicated/Severe Cellulitis Requiring MRSA Coverage

Empirical MRSA coverage is mandatory for hospitalized patients with complicated skin and soft tissue infections, defined as deeper infections, surgical/traumatic wounds, major abscesses, or infected ulcers/burns. 1

Approved IV options for MRSA coverage include:

• Vancomycin (first-line choice) 1
• Linezolid 600 mg IV twice daily 1
• Daptomycin 4 mg/kg IV once daily 1, 3
• Telavancin 10 mg/kg IV once daily 1
• Clindamycin 600 mg IV three times daily (if local resistance <10%) 1

Severe Infections with Systemic Toxicity

Broad-spectrum combination therapy is mandatory for patients with signs of systemic toxicity, rapid progression, or suspected necrotizing fasciitis. 2

Recommended IV combination regimens:

• Vancomycin or linezolid PLUS piperacillin-tazobactam 2
• Vancomycin or linezolid PLUS a carbapenem 2
• Vancomycin or linezolid PLUS ceftriaxone and metronidazole 2
• For documented group A streptococcal necrotizing fasciitis: penicillin PLUS clindamycin 2

Specific Clinical Scenarios

Penetrating Trauma or Purulent Drainage

Combination therapy providing both streptococcal and MRSA coverage is appropriate when cellulitis is associated with penetrating trauma, purulent drainage, or MRSA risk factors (injection drug use, known MRSA colonization, prior MRSA infection). 2, 4

Bite-Associated Cellulitis

For cellulitis from human or animal bites, use amoxicillin-clavulanate (Augmentin) 875/125 mg IV equivalent dosing, as it provides single-agent coverage for both streptococci and oral flora. 2

Treatment Duration

The standard treatment duration is 7-14 days for hospitalized patients with complicated cellulitis, but this should be shortened if rapid clinical improvement occurs. 1

• Recent evidence supports 5-day courses when clinical improvement is evident 2, 5, 6
• Extension beyond 5 days is only necessary if symptoms have not improved 2, 4
• Traditional 7-14 day courses are no longer necessary for uncomplicated cases 2

Common Pitfalls to Avoid

Do not routinely add MRSA coverage to beta-lactam therapy in typical nonpurulent cellulitis, as combination therapy provides no additional benefit and beta-lactam monotherapy succeeds in 96% of cases. 2, 7

• The addition of trimethoprim-sulfamethoxazole to cephalexin showed no improvement in outcomes in a randomized controlled trial 7
• Reserve MRSA coverage for specific risk factors: purulent drainage, penetrating trauma, known MRSA colonization, injection drug use, or failure of beta-lactam therapy 2, 4

Do not obtain blood cultures or tissue aspirates routinely in typical cellulitis cases. 4

• Blood cultures are indicated only for patients with malignancy, severe systemic features, or unusual predisposing factors 4

Do not neglect adjunctive measures that hasten recovery. 2, 4

• Elevation of the affected extremity promotes drainage and accelerates improvement 2, 4
• Examine and treat interdigital toe web spaces for fissuring, scaling, or maceration that may harbor pathogens 4
• Address predisposing conditions: edema, obesity, venous insufficiency, tinea pedis 2, 4

Pediatric Considerations

For hospitalized children with complicated cellulitis, vancomycin is the recommended first-line agent. 1

• If the patient is stable without ongoing bacteremia, clindamycin 10-13 mg/kg IV every 6-8 hours is an option if local clindamycin resistance is <10% 1
• Linezolid dosing: 600 mg IV twice daily for children >12 years; 10 mg/kg IV every 8 hours for children <12 years 1
• Never use tetracyclines (including doxycycline) in children <8 years of age due to tooth discoloration and bone growth effects 1, 2