Vancomycin Antibiotic Properties

Vancomycin: Introduction

• 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.

Administration

• 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.

Therapeutic and Toxic Plasma Concentrations

• 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.

Therapeutic and Toxic Plasma Concentrations (continued)

• 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.

Side Effects and Toxicity

• 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.

Bioavailability

• Oral bioavailability of vancomycin is poor.