Vancomycin is a tricyclic glycopeptide antibiotic derived from *Amycolatopsis orientalis*. It is a bactericidal agent primarily used for serious, life-threatening Gram-positive bacterial infections, particularly those caused by methicillin-resistant *Staphylococcus aureus* (MRSA) and other multidrug-resistant organisms. In the Indian context, it is a critical last-line antibiotic, heavily regulated to prevent resistance. It is poorly absorbed orally and is primarily administered intravenously for systemic infections; an oral formulation is used only for *Clostridioides difficile* colitis.
Adult: **IV for normal renal function (CrCl >90 mL/min):** 15-20 mg/kg/dose (actual body weight) every 8-12 hours. A typical 500mg dose is often used for a 60-70kg patient. **Loading dose:** 25-30 mg/kg may be used in critically ill patients to rapidly achieve target trough levels. **Oral for *C. difficile*:** 125 mg orally four times daily for 10 days (standard dose; 500mg oral dose is not standard and may be used in severe/complicated cases as per IDSA guidelines).
Note: **IV Administration:** MUST be infused slowly. 500mg should be diluted in at least 100 mL of compatible fluid (NS, D5W) and infused over **at least 60 minutes** (minimum 1 hour) to minimize risk of 'Red Man Syndrome' and phlebitis. Faster infusions (e.g., over 30 min) may be used in some protocols with pre-medication. **Oral Administration:** For *C. difficile*, the oral solution is prepared from the IV powder and must be taken as directed, not for systemic infection.
Vancomycin inhibits the second stage of cell wall synthesis in Gram-positive bacteria by binding with high affinity to the D-alanyl-D-alanine terminus of cell wall precursor units (lipid II). This binding prevents the transglycosylation and transpeptidation reactions catalyzed by penicillin-binding proteins (PBPs), thereby inhibiting peptidoglycan polymerization and cross-linking. This leads to weakening of the cell wall and ultimately causes bacterial cell lysis and death.
Pregnancy: **FDA Pregnancy Category C (US).** Crosses the placenta. Use only if clearly needed and potential benefit justifies potential risk to the fetus. No adequate, well-controlled studies in pregnant women. Considered an option for treating MRSA infections in pregnancy when no safer alternative exists.
Driving: Unlikely to affect driving ability. However, ototoxicity (vertigo) or severe dizziness from other causes could impair performance.
| Aminoglycosides (Gentamicin, Amikacin) | Additive/synergistic nephrotoxicity and ototoxicity. | Major |
| Loop Diuretics (Furosemide, Torsemide) | Increased risk of ototoxicity. | Major |
| Amphotericin B | Increased risk of nephrotoxicity. | Major |
| NSAIDs (e.g., Ibuprofen, Diclofenac) | Increased risk of nephrotoxicity. | Moderate |
| Anesthetic agents | May enhance neuromuscular blockade. | Moderate |
| Cholestyramine, Colestipol | May bind oral vancomycin in GI tract, reducing efficacy for *C. difficile* if administered concurrently. | Moderate |