Vancomycin: Glycopeptide Antibiotic for MRSA and C. difficile
Vancomycin is a glycopeptide antibiotic that inhibits bacterial cell wall synthesis by binding to the D-Ala-D-Ala terminus of peptidoglycan precursors. It remains the cornerstone of MRSA (methicillin-resistant Staphylococcus aureus) treatment and oral treatment of C. difficile infection (CDI).
IV form for systemic MRSA infections, bacteraemia, endocarditis, meningitis. Oral form (NOT absorbed) for C. difficile colitis — oral vancomycin treats gut infection directly.
Mechanism of Action
Binds to D-Ala-D-Ala terminus of lipid II (peptidoglycan precursor), blocking transglycosylation and transpeptidation — inhibits cell wall synthesis. Not affected by beta-lactamases. Bactericidal but concentration-independent (AUC/MIC-dependent). Not active against Gram-negative bacteria (outer membrane barrier).
Indications & Use
IV: MRSA bacteraemia, endocarditis, bone/joint infections, meningitis (with cephalosporin for pneumococcal), hospital-acquired MRSA pneumonia, febrile neutropaenia (penicillin-allergic). Oral: C. difficile infection (especially severe/recurrent). NOT for empirical UTI (poor urinary levels with standard dosing).
Dosage
IV: 15–20 mg/kg every 8–12 hours. Target AUC/MIC 400–600 mg·h/L (AUC-guided dosing preferred over trough monitoring). Loading dose 25–30 mg/kg for severe infections. Oral CDI: 125 mg 4× daily for 10 days. Renal dose adjustment essential — TDM (therapeutic drug monitoring) mandatory.
Side Effects
Nephrotoxicity (most important — especially with aminoglycosides; monitor creatinine). Red man syndrome (flushing, erythema — infusion-related, not allergy — slow infusion rate). Ototoxicity (hearing loss — rare, high concentrations). Phlebitis at infusion site.
Drug Interactions
Aminoglycosides (gentamicin, tobramycin): synergistic activity against enterococci, but additive nephrotoxicity — monitor. NSAIDs: increase nephrotoxicity risk. Neuromuscular blocking agents: vancomycin may enhance blockade.
Contraindications
Hypersensitivity to vancomycin. Not for empirical treatment when less broad-spectrum options are appropriate. IV contraindicated in patients with severe deafness (ototoxicity risk).
Frequently Asked Questions
What is 'Red Man Syndrome' and is it an allergy?
Red man syndrome is an infusion-related reaction (flushing, erythema, itching, hypotension) caused by mast cell degranulation — not IgE-mediated allergy. It is rate-dependent: slow the infusion to 60+ minutes (or 90 minutes for large doses). Premedication with antihistamine prevents recurrence.
Why is oral vancomycin used for C. difficile but not other infections?
Oral vancomycin is not absorbed from the gut — it achieves very high local concentrations in the colon where C. difficile lives. It is ineffective for systemic infections because oral bioavailability is <5%. This is a unique therapeutic property.
What is vancomycin-resistant Enterococcus (VRE)?
VRE are Enterococcus faecium or faecalis strains carrying van genes (vanA, vanB) that modify the D-Ala-D-Ala target so vancomycin cannot bind. VRE infections are treated with linezolid or daptomycin. VRE is a major concern in hospitals.
References
- EMA Vancomycin SPC 2023
- IDSA CDI Guidelines 2021
- EUCAST VRE Breakpoints 2023
Medical Disclaimer: This information is for educational purposes only and does not replace professional medical advice.