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Vancomycin Glycopeptides

Vancomycin and teicoplanin are the only members of this class of antibiotics. Vancomycin is a high-molecular-weight glycopeptide that is bactericidal for gram-positive microorganisms. It inhibits cell-wall synthesis. Given parenterally, it is the drug of choice for methicillin-resistant staphylococcal infections. It should be used as an alternative for methicillin-sensitive staphylococci if the patient is allergic to penicillin.

Vancomycin is also active against strains of penicillin-resistant S. pneumoniae, Leuconostoc spp., and Pediococcus spp. Some strains of Lactobacillus, Staphylococcus haemolyticus, and enterococci are resistant to vancomycin. Based on considerable clinical experience, there is a lack of clinical evidence to use combinations of aminoglycosides or rifampin with parenteral vancomycin to treat staphylococcal infections. However, treatment of serious enterococcal infections with vancomycin requires the synergistic bactericidal effects of an aminoglycoside to eradicate microorganisms outside the urinary tract.

Administered orally, vancomycin is poorly absorbed. However, the concentration of vancomycin in the gastrointestinal tract after an oral dose of 125 mg given every 6 hours is sufficient to eradicate — within 5 days of treatment — strains of C. difficile responsible for antibiotic-associated colitis.

Vancomycin is excreted by the kidneys in an essentially unchanged form. Vancomycin accumulates in patients with renal failure, and dosage adjustments are required to reduce the chances of adverse effects. Nephrotoxicity attributed to this agent has decreased remarkably because of improvements in the purification procedures in production of this drug. There are no data to suggest that monitoring serum vancomycin concentrations improves the effectiveness of therapy.

Furthermore, safe and effective vancomycin-dosing regimens can be derived empirically, taking into account the patient’s age, weight, and renal function (Cantu et al. 1994). The risk of nephrotoxicity with vancomycin is enhanced when drugs such as aminoglycosides or ethacrynic acid are given concomitantly. Ototoxicity in the form of tinnitus, high-tone hearing loss, and deafness is an important adverse reaction to vancomycin. The hearing loss occasionally improves when the drug is discontinued, but unfortunately it is usually permanent.

A “red man syndrome” characterized by hypotension and a maculopapular rash on the chest occurs if the drug is administered too quickly (e.g., over less than 30 minutes). If the infusion of vancomycin is prolonged (i.e., one gram infused over at least 60 minutes), the incidence of this syndrome is decreased.

Teicoplanin (not FDA approved at this point) has a spectrum of activity similar to that of vancomycin but with activity 2 to 4 times as high against sensitive organisms (except for diphtheroids). Some strains of coagulase-negative staphylococci are resistant to teicoplanin and sensitive to vancomycin. Teicoplanin is also effective against Clostridium difficile colitis when given orally.

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