Vancomycin Antibiotic Assay

General Information

Antimicrobial drugs normally have a high therapeutic index with supratherapeutic doses given safely (e.g. penicillins, macrolides, sulphonamides). The situation is different for aminoglycosides and some glycopeptides, which may cause significant toxicity just above the concentration required for bactericidal activity. 

Vancomycin is a glycopeptide active only against aerobic and anaerobic Gram-positive organisms. It is given intravenously in the prophylaxis and treatment of endocarditis and other serious infections caused by Gram-positive cocci including multi-resistant Staphylococcus aureus (MRSA). As with the aminoglycosides, nephrotoxicity and ototoxicity may occur at plasma concentrations above the therapeutic range. The risks are enhanced if aminoglycosides are given at the same time. The most common adverse reaction, flushing of the upper body (‘red man’ syndrome) occurs if the drug is infused too rapidly or too high a plasma concentration is attained. Toxicity is related to higher levels with this agent and again, it is the pre-dose level which should be monitored. Pre-doses are more reliable to monitor, as vancomycin has to be infused over at least an hour, causing post-dose levels to be more variable. Therefore post-dose vancomycin levels are not tested.