Vancomycin Therapy

Vancomycin is bactericidal against susceptible gram-positive organisms. It binds the D-alanine-D-alanine termini of peptidoglycan precursors, blocking bacterial cell-wall synthesis. This mechanism explains both its usefulness against resistant gram-positive pathogens such as MRSA and its lack of activity against most gram-negative organisms, whose outer membrane limits access to the drug’s target. Intravenous vancomycin is used for severe or life-threatening infections such as MRSA bacteraemia, endocarditis, osteomyelitis, and pneumonia. Oral vancomycin is used for *Clostridioides difficile* colitis, where the drug acts within the intestinal lumen. The oral formulation is not a substitute for intravenous therapy in bacteraemia, endocarditis, or another systemic infection. The kidneys clear most vancomycin. A dose that is appropriate when renal function is stable can become excessive when clearance falls, so kidney trends and drug levels must be interpreted together. The purpose of therapeutic drug monitoring is not to obtain the highest possible concentration; it is to maintain effective exposure without adding preventable toxicity.