Why is oral (PO) Vancomycin given for C. Difficile? Why not IV?
MECHANISM: Vancomycin is a large, hydrophilic molecule that for the most part is not absorbed across the gastrointestinal mucosa (it has low bioavailability).
Hence when given PO, it will accumulate in the GI tract and reach sufficient concentrations for therapeutic effect against C. Difficile.
When given via IV, it undergoes extensive “1st pass” metabolism in the liver with very little bioavailability.
1. Van Bambeke F (August 2006). “Glycopeptides and glycodepsipeptides in clinical development: a comparative review of their antibacterial spectrum, pharmacokinetics and clinical efficacy”. Current Opinion in Investigational Drugs 7 (8): 740–9.
2. Edlund C, Barkholt L, Olsson-Liljequist B, Nord CE (September 1997). “Effect of vancomycin on intestinal flora of patients who previously received antimicrobial therapy”. Clinical Infectious Diseases 25 (3): 729–32.
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