Glycopeptide antibiotic · MRSA, C. diff
A long-established antibiotic for serious infections caused by Gram-positive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA). Given into a vein, it treats bloodstream, heart-valve, bone, skin and lower respiratory infections. Taken by mouth, it stays mostly in the gut and is used for Clostridioides difficile diarrhea and staphylococcal enterocolitis.
Vancomycin targets the bacterial cell wall rather than a protein. It forms a tight network of hydrogen bonds with the D-Ala-D-Ala end of lipid II, a building block of peptidoglycan, which stops the wall from maturing and kills the bacterium3. The label adds that it also alters membrane permeability and RNA synthesis1. It is not active against Gram-negative bacilli, mycobacteria or fungi1. Swallowed vancomycin is poorly absorbed, so it acts mainly inside the bowel: the oral form treats C. difficile colitis but not infections elsewhere, and the intravenous form does not work for C. difficile2. Resistance arises when bacteria replace D-Ala-D-Ala with D-Ala-D-Lac or D-Ala-D-Ser, which vancomycin binds poorly3.
Vancomycin entered clinical use more than half a century ago but was soon set aside for antibiotics considered more effective and less toxic. It came back into wide use as MRSA spread and C. difficile colitis became common, and resistance then emerged, first in enterococci and later in staphylococci4. Much of the modern human evidence compares it with other drugs.
In a double-blind trial of 172 patients with C. difficile diarrhea, oral vancomycin and metronidazole cured similar shares of mild cases (98% vs 90%), but vancomycin did better in severe disease (97% vs 76%)5. In a phase 3 trial of 629 adults, fidaxomicin matched vancomycin for clinical cure (88.2% vs 85.8%) but had fewer recurrences (15.4% vs 25.3%)6.
In the two C. difficile trials described in the oral label (266 adults), about 81% reached clinical success by day 10, and about one in five responders relapsed within four weeks2.
FDA-approved for decades and widely available as generics. Injectable products are approved for septicemia, endocarditis, skin, bone and lower respiratory infections caused by susceptible Gram-positive bacteria; oral Vancocin and generics are approved for C. difficile-associated diarrhea and staphylococcal enterocolitis.
Per the FDA labels, rapid intravenous infusion can cause a 'vancomycin infusion reaction' (itching and flushing of the face, neck and upper body) and, less often, low blood pressure or shock. Warnings cover kidney injury, hearing loss and tinnitus, severe skin reactions (SJS, TEN, DRESS), C. difficile diarrhea, low white-cell counts and vein irritation. With oral use, nausea, abdominal pain and low potassium are most common; kidney injury and hearing effects can still occur.
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