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Vancomycin is a glycopeptide antibiotic primarily used to treat serious bacterial infections caused by Gram-positive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA). Understanding its pharmacokinetics is essential for optimizing therapy and minimizing toxicity.
Absorption of Vancomycin
Vancomycin has poor oral bioavailability, which means it is not effectively absorbed when taken orally. As a result, it is usually administered intravenously for systemic infections. Oral vancomycin is mainly used to treat Clostridioides difficile infections within the gastrointestinal tract.
Distribution of Vancomycin
After intravenous administration, vancomycin distributes primarily in the extracellular fluid and has a volume of distribution (Vd) of approximately 0.4 to 1 L/kg. It penetrates various tissues, including the lungs, kidneys, liver, and bones, but has limited penetration into the cerebrospinal fluid unless the meninges are inflamed.
Metabolism of Vancomycin
Vancomycin undergoes minimal metabolism in the body. It remains largely unchanged as it circulates, which simplifies its pharmacokinetic profile and reduces the risk of metabolic interactions. Its elimination is primarily through renal excretion.
Excretion of Vancomycin
Renal excretion is the main route of vancomycin elimination. It is eliminated via glomerular filtration, with negligible tubular reabsorption or secretion. The half-life of vancomycin varies depending on renal function, typically around 6 to 12 hours in patients with normal renal function.
Clinical Implications
Understanding vancomycin pharmacokinetics is crucial for dosing, especially in patients with impaired renal function. Therapeutic drug monitoring (TDM) is often employed to maintain effective serum concentrations while minimizing toxicity, such as nephrotoxicity and ototoxicity.
Summary
- Absorption: Poor oral absorption; mainly IV use
- Distribution: Extracellular fluid, tissues, limited CSF penetration
- Metabolism: Minimal, unchanged in circulation
- Excretion: Renal elimination via glomerular filtration