Vancomycin
At a Glance
Why Get Tested?
To measure and monitor the concentration of vancomycin in the blood
When to Get Tested?
At intervals during vancomycin treatment
Sample Required?
A blood sample taken from a vein in your arm
The Test Sample
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 meticillin, but has risen again with the emergence of meticillin-resistant strains of staphylococcus, such as staphylococcus aureus (Meticillin Resistant Staphylococcus Aureus, MRSA).
Intravenous vancomycin may be given to treat infections such as septicaemia (infection of the blood), endocarditis (infection of the membrane surrounding the heart), osteomyelitis (infection of the bone), some pneumonias, and meningitis (infection of the spinal cord). It is often the drug of choice for meticillin-resistant staphylococcus epidermidis and staphylococcus aureus infections, especially when they are associated with implanted devices such as heart valves, artificial hips, and indwelling catheters. Vancomycin may also be given to prevent an infection (prophylactically) to some people before specific surgeries and dental procedures. Intravenous vancomycin administration is necessary to get drug into the circulation because oral vancomycin is poorly absorbed through the intestine. Oral vancomycin is prescribed to treat some resistant clostridium difficile infections, which occur in the gastrointestinal tract where absorption into the circulation is not needed.
The effectiveness of vancomycin depends on maintaining blood levels at a minimum concentration for the duration of therapy. Excessive concentrations of vancomycin must be avoided because high levels can result in damage to some organs, specifically ototoxicity (damage to hearing) and nephrotoxicity (kidney damage). The amount of vancomycin given in each dose depends on a variety of factors, including how well the kidney is functioning, the presence of other drugs which might have casue kidney damage and the patient’s age and weight.
A patient with decreased kidney function may not be able to remove all of the drug from their system which will cause an 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.
How is the sample collected for testing?
A blood sample is obtained by inserting a needle into a vein in the arm.
NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.
Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.
The Test
How is it used?
When a vancomycin dose is given, its concentration rises in the blood, peaks, and then falls. The next dose is timed to be given in anticipation of the falling level. The goal is to overlap the doses enough so that a minimum concentration is always maintained in the blood. Measurement of blood levels is requested at times that reflect the lowest concentration (trough) and the highest concentration (peak) to evaluate the effectiveness of therapy. Trough levels are collected just prior to a patient’s next vancomycin dose. Peak levels are collected 1 to 2 hours after the completion of the intravenous vancomycin dose. The trough and peak values are used by clinical pharmacists and doctors to calculate rates of absorption and clearance of the drug. These results are then used to determine the appropriate amount of drug and the appropriate timing between doses to assure that the blood concentration remains in the therapeutic range.
For additional information on how the test is used, see Therapeutic Drug Monitoring.
When is it requested?
There is not a widespread consensus on the use of the vancomycin test. Some doctors will request trough levels every few days throughout vancomycin treatment. Some will request both trough and peak concentrations at regular intervals. Many do not feel that general monitoring is necessary and will only request the tests on patients who are at increased risk of kidney damage because of other medicine that they are taking, poor kidney function. They may also use the test on those who are not responding to treatment as expected.
What does the test result mean?
If trough levels of vancomycin are above the minimum level, then the patient should be receiving enough of the drug to be effective. If the patient’s infection is not responding to the treatment, then the doctor may either continue the drug for a longer period of time or consider other treatment options. If peak concentrations are below maximum levels, then the patient is at less risk of developing nephrotoxicity and/or ototoxicity (but may still experience either complication). Peak concentrations may vary, depending on the consistency of collection timing and on changing drug clearance rates. If the peak concentration is excessive, the doctor may either alter the dose or alter the dosing schedule.
Is there anything else I should know?
An intravenous vancomycin dose must be given slowly. Patients given the dose at a rapid rate are at an increased risk of developing “red man syndrome,” a histamine reaction that causes flushing of the face, a rash on the upper body, and a significant drop in blood pressure.
Kidney function tests such as urea, creatinine and creatinine clearance may be ordered prior to the start of vancomycin therapy and at intervals, or as needed, to evaluate changes in kidney status.
Common Questions
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Article Sources
NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.
