Vancomycin — Use & Administration
Vancomycin is a frontline weapon against MRSA — but give it wrong, and you create the very resistance you're trying to fight. Knowing when and how to use it is non-negotiable.
Core Concept
Vancomycin is a glycopeptide antibiotic that kills gram-positive bacteria by inhibiting cell wall synthesis — it binds to the D-alanyl-D-alanine terminus of peptidoglycan precursors, preventing cross-linking. This mechanism makes it the drug of choice for serious MRSA infections (bacteremia, endocarditis, osteomyelitis, pneumonia) and for treating Clostridioides difficile colitis when given orally. IV vancomycin treats systemic infections because it is not absorbed from the GI tract. Oral vancomycin stays in the gut, which is exactly why it works for C. diff — it reaches the site of infection directly. Standard IV infusion runs over at least 60 minutes (often longer for doses above 1 g) to prevent infusion-related reactions. Dosing is weight-based, and trough levels guide therapy — the target AUC/MIC approach or trough of 15–20 mcg/mL for serious infections ensures adequate bactericidal activity while limiting harm. Troughs are drawn 30 minutes before the fourth or fifth dose at steady state.
Watch Out For
Oral vancomycin treats C. diff only — it does NOT treat systemic infections because it isn't absorbed. IV vancomycin treats systemic MRSA infections but does not achieve adequate gut lumen concentrations for standard C. diff treatment (IV vancomycin may be added as adjunctive therapy in fulminant C. diff). Students commonly confuse the route-indication pairing and select IV vancomycin for C. diff, which is incorrect for non-fulminant disease. Don't confuse vancomycin (cell wall synthesis inhibitor, gram-positive only) with aminoglycosides (protein synthesis inhibitors, gram-negative coverage).
Clinical Pearl
Mouth for the gut, vein for the body. Oral vancomycin stays local for C. diff; IV vancomycin goes systemic for MRSA. Wrong route = wrong infection.
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