Vancomycin

Vancomycin

Vancomycin hydrochloride is used increasingly to treat methi-cillin-resistant S. aureus, which has become a major concern in the United States and other parts of the world. Because of the emergence of vancomycin-resistant enterococci, vancomycin must be used judiciously. As a rule of thumb, it should be used only when culture and sensitivity test results confirm the need for it.

Pharmacokinetics

Because vancomycin is absorbed poorly from the GI tract, it must be given I.V. to treat systemic infections. However, an oral form of vancomycin is used to treat pseudomembranous colitis. Van-comycin diffuses well into pleural (around the lungs), pericardial (around the heart), synovial (joint), and ascitic (in the peritoneal cavity) fluids.

No switching!

Remember that I.V. vancomycin can’t be used in place of oral van-comycin and vice versa. The two forms aren’t interchangeable.

Metabolism and excretion

The metabolism of vancomycin is unknown. About 85% of the dose is excreted unchanged in urine within 24 hours. A small amount may be eliminated through the liver and biliary tract.

Pharmacodynamics

Vancomycin inhibits bacterial cell-wall synthesis, damaging the bacterial plasma membrane. When the bacterial cell wall is damaged, the body’s natural defenses can attack the organism.

Pharmacotherapeutics

Vancomycin is active against gram-positive organisms, such as S. aureus, S. epidermidis, S. pyogenes, Enterococcus, and S. pneumoniae.

In the I.V. league

I.V. vancomycin is the therapy of choice for the patient with a seri-ous resistant staphylococcal infection who’s hypersensitive to penicillins.

Oral history

Oral vancomycin is used for the patient with antibiotic-associated Clostridium difficile colitis who can’t take or has respondedpoorly to metronidazole.

The 1 in the 1-2 punch

Vancomycin, when used with an aminoglycoside, is also the treat-ment of choice for E. faecalis endocarditis in the patient who’s al-lergic to penicillin.

Drug interactions

Vancomycin may increase the risk of toxicity when administered with other drugs toxic to the kidneys and organs of hearing, such as aminoglycosides, amphotericin B, bacitracin, cisplatin, colistin, and polymyxin B. (See Adverse reactions to vancomycin.)