indication

For the treatment of serious or severe infections caused by susceptible strains of methicillin-resistant (beta-lactam-resistant) staphylococci.

pharmacology

Vancomycin is a branched tricyclic glycosylated nonribosomal peptide produced by the fermentation of the Actinobacteria species Amycolatopsis orientalis (formerly Nocardia orientalis). It is often reserved as the "drug of last resort", used only after treatment with other antibiotics had failed. Vancomycin has been shown to be active against most strains of the following microorganisms, both in vitro and in clinical infections: Listeria monocytogenes, Streptococcus pyogenes, Streptococcus pneumoniae (including penicillin-resistant strains), Streptococcus agalactiae, Actinomyces species, and Lactobacillus species. The combination of vancomycin and an aminoglycoside acts synergistically in vitro against many strains of Staphylococcus aureus, Streptococcus bovis, enterococci, and the viridans group streptococci.

mechanism of action

The bactericidal action of vancomycin results primarily from inhibition of cell-wall biosynthesis. Specifically, vancomycin prevents incorporation of N-acetylmuramic acid (NAM)- and N-acetylglucosamine (NAG)-peptide subunits from being incorporated into the peptidoglycan matrix; which forms the major structural component of Gram-positive cell walls. The large hydrophilic molecule is able to form hydrogen bond interactions with the terminal D-alanyl-D-alanine moieties of the NAM/NAG-peptides. Normally this is a five-point interaction. This binding of vancomycin to the D-Ala-D-Ala prevents the incorporation of the NAM/NAG-peptide subunits into the peptidoglycan matrix. In addition, vancomycin alters bacterial-cell-membrane permeability and RNA synthesis. There is no cross-resistance between vancomycin and other antibiotics. Vancomycin is not active in vitro against gram-negative bacilli, mycobacteria, or fungi.

toxicity

The oral LD₅₀ in mice is 5000 mg/kg. The median lethal intravenous dose is 319 mg/kg in rats and 400 mg/kg in mice.

absorption

Poorly absorbed from gastrointestinal tract, however systemic absorption (up to 60%) may occur following intraperitoneal administration.

half life

Half-life in normal renal patients is approximately 6 hours (range 4 to 11 hours). In anephric patients, the average half-life of elimination is 7.5 days.

route of elimination

In the first 24 hours, about 75% of an administered dose of vancomycin is excreted in urine by glomerular filtration.

drug interactions

Colistimethate: Additive nephrotoxic effects may occur. Consider alternate therapy or monitor for renal function during concomitant therapy.

Gallium nitrate: Additive nephrotoxic effects may occur. Avoid concomitant therapy.

Tobramycin: Increased risk of nephrotoxicity