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Vancomycin

EvidenceFDA approved

ClassGlycopeptide antibiotic

Vancomycin is an FDA-approved antibiotic for serious Gram-positive infections, including MRSA and C. difficile. Learn how it works, its uses, and side effects.

Reviewed by: William Maish, MD MBA MPH, Clinical Product Lead
Published: October 5, 2026
Last updated: October 5, 2026

Key takeaway

Vancomycin (sold as a generic injection and, for oral use, as Vancocin and Firvanq) is a glycopeptide antibiotic that has been a mainstay against serious Gram-positive infections, including MRSA, for decades. It kills bacteria by blocking construction of their cell wall, and the same drug, taken by mouth, treats intestinal C. difficile infection. It has been FDA-approved in the U.S. since 1958 and is given intravenously for most infections or orally for gut infections.

At a glance

What it is	A glycopeptide antibiotic active against Gram-positive bacteria
Approved for	Serious MRSA and other Gram-positive infections (intravenous); C. difficile-associated diarrhea (oral)
Key fact	It remains the standard comparator against which newer anti-MRSA drugs are measured
Route	Intravenous for systemic infection; oral (not absorbed) for intestinal infection
Evidence strength	FDA approved

What is vancomycin?

Vancomycin, sold as a generic injection and as the oral products Vancocin (capsules) and Firvanq (oral solution), is a glycopeptide antibiotic, a large, complex molecule that bacteria have found relatively hard to resist. It is used for serious infections caused by Gram-positive bacteria, especially methicillin-resistant Staphylococcus aureus (MRSA), and it has a distinct second role: taken orally, where it stays in the gut, it treats Clostridioides difficile infection. It was approved in the United States in 1958.

The history of vancomycin

Vancomycin came from a soil bacterium collected in the 1950s, at a time when penicillin resistance in staphylococci was becoming a serious problem. The earliest preparations were impure and brown, earning the nickname "Mississippi mud," and early formulations were associated with more side effects than the purified drug used today. For years it was held in reserve, but with the spread of MRSA it became one of the most important last-resort antibiotics in the hospital, a role it still holds more than six decades after approval.

How does vancomycin work?

Vancomycin blocks bacterial cell-wall synthesis. It binds tightly to the building blocks of peptidoglycan, the mesh that gives the bacterial wall its strength, specifically the D-alanyl-D-alanine end of those precursors. By capping that site, it prevents the cross-linking that would complete the wall, so the growing bacterium cannot maintain its structure and dies. This is a different target from the penicillins, which is why vancomycin works against many penicillin-resistant organisms.

Where it acts depends on the form given:

Form	Where it acts	Infections treated
Intravenous	Distributes through the body	Bloodstream, bone, skin, and other serious Gram-positive infections
Oral	Barely absorbed, so it acts locally in the intestine	C. difficile, where local action is exactly what is wanted

Dosing is guided by blood levels, because too little risks treatment failure and resistance while too much raises the risk of kidney injury. Vancomycin is established enough that newer drugs are tested against it. In a 2006 trial in Staphylococcus aureus bloodstream infection, daptomycin was compared with standard therapy¹ that included vancomycin.

Is it FDA-approved?

Yes. Vancomycin has been FDA-approved² since 1958 and is available as intravenous formulations and an oral form. Its approved uses span serious Gram-positive infections systemically and C. difficile infection and staphylococcal enterocolitis when given orally.

What is vancomycin prescribed for?

Intravenous vancomycin is prescribed for serious Gram-positive infections such as MRSA bloodstream infections, endocarditis, bone and joint infections, skin and soft-tissue infections, and pneumonia. Oral vancomycin is prescribed for C. difficile-associated diarrhea, where it acts within the gut.

What are the side effects?

According to the prescribing information, common side effects of intravenous vancomycin include:

Kidney injury
Hearing loss
Low white-cell counts
Allergic reactions
Vancomycin infusion reaction, a flushing reaction related to fast infusion (formerly called "red man syndrome")

Common side effects of oral vancomycin include:

Nausea
Abdominal pain
Low potassium

More serious considerations include:

Severe skin reactions
Lasting kidney or hearing damage, more likely at high blood levels or with other drugs that stress the kidneys

More for heart & blood

Sources: FDA prescribing information for vancomycin injection, Vancocin, and Firvanq; a trial of daptomycin versus standard therapy that included vancomycin (Fowler et al., The New England Journal of Medicine, 2006, DOI: 10.1056/NEJMoa053783¹), indexed on PubMed. This document is educational and does not constitute medical advice.