What is being tested?This test measures the concentration of vancomycin in the blood. Vancomycin is an antimicrobial that is used to treat serious infections caused by
gram-positive bacteria. Developed in the 1950s, vancomycin was originally prescribed primarily when organisms proved resistant to penicillin or when a person was allergic to penicillin. Its use declined with the introduction of other antimicrobials such as methicillin, but has risen again with the emergence of methicillin-resistant strains of Staphylococcus, such as
Staphylococcus aureus.
Intravenous vancomycin may be given to treat infections such as septicemia, endocarditis (infection of the membrane surrounding the heart), osteomyelitis (infection of the bone), some pneumonias, and meningitis. It is often the drug of choice for methicillin-resistant Staphylococcus epidermidisand Staphylococcus aureus infections, especially when they are associated with implanted prosthetic devices such as heart valves, artificial hips, and indwelling catheters. Vancomycin may also be given prophylactically (to prevent an infection) to some people before specific surgeries and dental procedures. Intravenous vancomycin administration is necessary to get drug into the circulation because the oral vancomycin is poorly absorbed. Oral vancomycin is prescribed to treat some resistant Clostridium difficile infections, infections that occur in the gastrointestinal tract where absorption into the circulation is not needed.
The effectiveness of vancomycin depends on sustaining blood levels at a minimum concentration for duration of therapy. Excessive concentrations of vancomycin must be avoided because high levels can result in toxicities - specifically ototoxicity (damage to hearing) and nephrotoxicity (kidney damage). The amount of vancomycin given per dose depends on a variety of factors, including kidney function, other nephrotoxic drugs the patient may be taking, age, and weight.
A patient with decreased kidney function may not be able to clear the drug out of his system efficiently, resulting in increased concentration in the blood. If a patient is given too little drug and is unable to maintain a sufficient minimum dose in the blood, then it is unlikely that treatment will be effective. The vancomycin test can be used to monitor the amount of drug in the blood to ensure that it is adequate but not excessive.
