Is mupirocin (Bactroban) effective for treating cellulitis?

Mupirocin is NOT Effective for Treating Cellulitis

Mupirocin should not be used to treat cellulitis—it is only indicated for superficial skin infections like impetigo and for nasal decolonization of Staphylococcus aureus carriers. 1

Why Mupirocin Fails in Cellulitis

Inadequate Tissue Penetration

• Mupirocin is formulated for topical use only and shows no measurable systemic absorption (<1.1 nanogram/mL in whole blood), with drug remaining confined to the stratum corneum. 2
• Cellulitis is a deeper infection involving the dermis and subcutaneous tissue, requiring systemic antibiotics that achieve therapeutic tissue levels. 1
• The FDA label explicitly states mupirocin's activity is limited to superficial applications, making it pharmacologically unsuitable for deeper infections. 2

Wrong Spectrum for Cellulitis Pathogens

• Typical cellulitis without purulent drainage is primarily caused by streptococci (especially Streptococcus pyogenes), which require systemic beta-lactam antibiotics. 1
• While mupirocin has activity against streptococci in vitro, the IDSA guidelines emphasize that cellulitis needs systemic antimicrobials active against streptococci as first-line therapy. 1

What to Use Instead for Cellulitis

Mild Cellulitis (Outpatient)

• Penicillinase-resistant penicillin (e.g., dicloxacillin) or first-generation cephalosporin (e.g., cephalexin) for typical cases. 1
• For penicillin-allergic patients: clindamycin (if local susceptibility permits) or a macrolide. 1
• Treatment duration: 5 days minimum, extending if no improvement. 1

Moderate to Severe Cellulitis

• If MRSA risk factors present (purulent drainage, injection drug use, penetrating trauma, known MRSA colonization): use vancomycin or another agent effective against both MRSA and streptococci. 1
• For severely immunocompromised patients: vancomycin plus piperacillin-tazobactam or imipenem-meropenem for broad coverage. 1

Where Mupirocin IS Appropriate

Impetigo (Superficial Infection)

• Mupirocin 2% ointment applied three times daily for 5 days is the best topical agent for localized, nonbullous impetigo. 1, 3
• Switch to oral antibiotics if numerous lesions present or no response within 3-5 days. 3

Nasal Decolonization for Recurrent Infections

• For recurrent S. aureus skin abscesses: intranasal mupirocin twice daily for 5 days combined with daily chlorhexidine washes. 1, 3
• This is an adjunctive strategy only—incision and drainage remains primary treatment for abscesses. 1, 3
• Approximately 15 grams needed for complete 5-day intranasal course. 3

Critical Clinical Pitfalls

Don't Confuse Superficial with Deep Infections

• Impetigo (honey-crusted lesions, very superficial) responds to topical mupirocin. 1
• Cellulitis (spreading erythema, warmth, deeper tissue involvement) requires systemic therapy—topical agents will fail. 1

Resistance Concerns

• High-level mupirocin resistance (MIC >512 µg/mL) has been reported in S. aureus, associated with decolonization failure. 1
• Complete the full 5-day course even if symptoms improve to minimize resistance development. 3

Adjunctive Measures for Cellulitis

• Elevate the affected extremity and treat predisposing factors like edema or tinea pedis (examine interdigital toe spaces). 1
• Re-evaluate patients in 24-48 hours if sent home on oral antibiotics to verify clinical response. 1