Oral Vancomycin is NOT Effective for Cellulitis
Oral vancomycin should never be used to treat cellulitis because it is not absorbed systemically from the gastrointestinal tract and therefore cannot reach infected skin and soft tissues. This is a fundamental pharmacokinetic principle that makes oral vancomycin completely ineffective for any systemic infection, including cellulitis.
Why Oral Vancomycin Fails for Cellulitis
Oral vancomycin remains in the gastrointestinal lumen and is not absorbed into the bloodstream, making it unable to reach skin and soft tissue infection sites 1.
The only approved indication for oral vancomycin is Clostridioides difficile infection (CDI), where the drug acts locally in the colon rather than systemically 1.
For cellulitis requiring vancomycin coverage, intravenous vancomycin 15-20 mg/kg every 8-12 hours is the appropriate route, providing systemic drug levels necessary to treat skin and soft tissue infections 2.
Correct Treatment Approach for Cellulitis
First-Line Therapy for Typical Cellulitis
Beta-lactam monotherapy is the standard of care for typical uncomplicated cellulitis, with a 96% success rate, confirming that MRSA coverage is usually unnecessary 2.
Recommended oral agents include cephalexin 500 mg four times daily, dicloxacillin 250-500 mg every 6 hours, amoxicillin, or penicillin 2.
Treatment duration is 5 days if clinical improvement occurs, extending only if symptoms have not improved within this timeframe 2.
When IV Vancomycin IS Appropriate
IV vancomycin is indicated for hospitalized patients with complicated cellulitis, particularly when MRSA coverage is needed 2.
Specific indications for MRSA-active therapy include purulent drainage, penetrating trauma, injection drug use, evidence of MRSA infection elsewhere, or systemic inflammatory response syndrome 2.
For severe cellulitis with systemic toxicity, vancomycin 15-20 mg/kg IV every 8-12 hours plus piperacillin-tazobactam 3.375-4.5 g IV every 6 hours provides broad-spectrum coverage 2.
Critical Pitfall to Avoid
Never prescribe oral vancomycin for cellulitis under any circumstances. This represents a fundamental misunderstanding of the drug's pharmacology and will result in treatment failure. If vancomycin coverage is truly needed for cellulitis, it must be administered intravenously 2, 3.