Vancomycin Antibiotic Properties

Study Notes

Vancomycin is an antibiotic effective against gram-positive bacteria, particularly nafcillin- or methicillin-resistant Staphylococcus aureus (NRSA or MRSA).
It is an alternative to penicillin in patients with a history of serious penicillin allergy.

Vancomycin is poorly absorbed orally and must be administered via intravenous route or intraperitoneally for patients receiving continuous ambulatory peritoneal dialysis (CAPD).
The usual adult dose is 1g (10 to 15 mg/kg) administered intravenously over 60 minutes every 8 to 12 hours.
Vancomycin is not administered intramuscularly due to pain, local irritation, and histamine reaction.

The ideal vancomycin plasma concentrations are less than 40 to 50 mg/L, with trough concentrations between 5 to 20 mg/L.
Peak concentrations greater than 50 mg/L have been associated with ototoxicity, particularly above 80 mg/L.
The minimum inhibitory concentration (MIC) for sensitive bacteria is less than 5 mg/L, with a limited postantibiotic effect of 0.5 to 3 hours.

The MIC for most strains of staphylococcus is less than 5 mg/L, and trough concentrations should be maintained between 5 to 15 mg/L.
Some clinicians recommend maintaining plasma trough concentrations above 10 mg/L for increased efficacy in patients with endocarditis.
Patients with nosocomial infections, pneumonia, and other systemic infections with MRSA having an MIC of 2.0 mg/L are at greater risk of therapeutic failure, and may require tailored doses to achieve trough concentrations of 15 to 20 mg/L or an AUC24/MIC ratio of 400.

The major side effects associated with vancomycin therapy include phlebitis and a histamine reaction presenting as flushing, tachycardia, and hypotension.
Vancomycin should be infused slowly over 60 minutes to minimize the histamine response.
Vancomycin is associated with a low incidence of nephrotoxicity as a single agent, but the incidence may increase when combined with aminoglycoside antibiotics.
Higher rates of nephrotoxicity have been observed when targeting trough vancomycin concentrations of 15 to 20 mg/L or maintaining high-dose therapy for 2 weeks or longer.