Vancomycin

• Brand names: Vancocin
• Route: Intravenous (oral capsules only for gut C. difficile)

Vancomycin is a glycopeptide. It binds tightly to the D-alanyl-D-alanine tail of the building blocks used to construct the bacterial cell wall, physically blocking the cross-linking step that gives the wall its strength.

Because it acts on a different target from the beta-lactams, the mecA-encoded PBP2a protein that makes MRSA resistant to methicillin and flucloxacillin does not protect the organism from vancomycin.

It kills slowly and penetrates tissue poorly compared with beta-lactams, which is why treatment of deep infection is measured in weeks rather than days.

• Typical adult intravenous dosing is 15–20 mg/kg of actual body weight every 8–12 hours, adjusted for kidney function. A loading dose of 20–35 mg/kg is often used in severe sepsis.
• Dosing is guided by therapeutic drug monitoring. Current guidance targets an AUC24/MIC ratio of 400–600, which has largely replaced simple trough targets of 15–20 mg/L.
• Each dose is infused over at least 60 minutes to reduce the risk of infusion reactions. Courses run from 7–14 days for uncomplicated bacteraemia up to 6 weeks for endocarditis or bone infection.
• Oral vancomycin is not absorbed and is used only for Clostridioides difficile colitis — it does not treat MRSA anywhere else in the body.

Doses listed are typical adult regimens quoted for reference. The actual dose, route and duration are decided by a clinician for the individual patient.

Vancomycin was isolated in 1953 by Eli Lilly chemists from Amycolatopsis orientalis, a soil organism in a sample sent from Borneo by a missionary. The name comes from 'vanquish'.

It was licensed in 1958 as a last-resort agent for penicillin-resistant staphylococci. Early impure preparations, nicknamed 'Mississippi mud', caused so much toxicity that it fell out of favour once methicillin arrived.

Purification in the 1970s and 1980s, together with the spread of MRSA, brought vancomycin back as the standard treatment for resistant staphylococcal infection.

• Infusion-related reaction (formerly 'red man syndrome'): flushing, rash and itching of the face and torso caused by histamine release when the drug is given too quickly. Slowing the infusion usually resolves it.
• Kidney injury, particularly with high exposures, prolonged courses, or when combined with piperacillin-tazobactam or other nephrotoxic drugs.
• Less common: hearing loss, low platelet or white cell counts, drug fever, phlebitis at the drip site, and rare severe skin reactions such as DRESS.

• Serious infections with other resistant Gram-positive bacteria: coagulase-negative staphylococci, ampicillin-resistant enterococci and penicillin-resistant pneumococci.
• Empirical cover in febrile neutropenia, prosthetic-device infection, and suspected central-line infection.
• Oral vancomycin is a first-line treatment for Clostridioides difficile infection.