To measure and monitor the level of vancomycin in your blood
At intervals during vancomycin treatment
A blood sample drawn from a vein in your arm
None, but timing of the sample for testing is important; samples are typically collected just before the next dose (trough level). Follow any instructions provided.
Vancomycin is an antibiotic that is used to treat serious infections caused by Gram-positive bacteria. This test measures the concentration of vancomycin in the blood.
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 certain strains of Staphylococcus, such as methicillin-resistant Staphylococcus aureus (MRSA).
It is important to monitor the level of vancomycin because its effectiveness depends on sustaining blood levels at a minimum concentration for the duration of therapy. Furthermore, excessive concentrations of vancomycin must be avoided because high levels can result in serious side effects, specifically hearing (ototoxicity) and kidney damage (nephrotoxicity). The amount of vancomycin given per dose depends on a variety of factors, including kidney function, other nephrotoxic drugs the person may be taking, age, and weight.
Decreased kidney function may prevent efficient clearance of vancomycin from a person's system, resulting in increased concentration in the blood. If a person 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 remains at a therapeutic concentration – that is, adequate but not excessive.
Vancomycin is given intravenously (by injection into a vein) to treat infections such as septicemia, endocarditis, infection of the bone (osteomyelitis), some pneumonias, and meningitis. It is often the drug of choice for methicillin-resistant Staphylococcus epidermidis and MRSA infections, especially when they are associated with implanted prosthetic devices such as heart valves, artificial hips, and indwelling catheters. Vancomycin may also be given to some people before specific surgeries and dental procedures to prevent an infection.
Intravenous vancomycin administration is necessary to get the drug into circulation because vancomycin taken as a pill by mouth (oral) is poorly absorbed in the digestive tract. However, oral vancomycin may be prescribed to treat some infections of the digestive tract, where absorption into the circulating blood is not needed. An example is Clostridium difficile infection.
How is it used?
This test is used to monitor levels of the antibiotic vancomycin in the blood. When a person takes a dose of vancomycin, the amount in the blood rises for a period of time, peaks, and then begins to fall, usually reaching its lowest level, or trough, just before the next dose. The next dose is timed to coincide with the falling concentration of the drug in the blood.
Because the goal is to administer the vancomycin such that a minimally effective concentration is always maintained in the blood, measurement of blood levels is usually timed to reflect the trough and, sometimes peak, to evaluate the adequacy of dosing and clearance of the drug from the body. Trough levels are collected just prior to a person's next vancomycin dose. Peak levels are collected 1 to 2 hours after the completion of the intravenous vancomycin dose.
The trough and sometimes peak values are used by clinical pharmacists and healthcare practitioners 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 ordered?
There is no widespread consensus on the use of the vancomycin test and when to order it. Some healthcare practitioners will order trough levels every few days throughout vancomycin treatment. Some will order both trough and peak concentrations at regular intervals. Many do not feel that general monitoring is necessary and will only order the tests for those who are at increased risk of kidney damage (nephrotoxicity), who are taking concurrent medications, who have decreased kidney function, or who are not responding to treatment as expected.
What does the test result mean?
Guidelines from 2009 by pharmacists and infectious disease specialists recommend that only trough levels be performed, with a minimum of 10 mcg/mL considered necessary to control an infection. The guidelines recommend a therapeutic range of 15-20 mcg/mL for significant infections. However, many institutions have specific ranges depending on the site of infection and severity of infection.
If trough levels of vancomycin are above the minimum level, then the person should be receiving enough of the drug to be effective. If the person's infection is not responding to the treatment, then the healthcare practitioner 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 treated person 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 trough and/or peak concentrations are above the maximum levels, then the person is at an increased risk of toxicity and the healthcare practitioner may either alter the dose or the dosing schedule.
Is there anything else I should know?
An intravenous vancomycin dose must be given slowly. People 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.
Why isn't vancomycin more widely used?
The medical community tries to be conservative in its use of vancomycin, reserving it for patients with few other treatment options to stave off the emergence of vancomycin-resistant microbes. In recent years, some resistant and intermediate (decreased sensitivity) strains of Staphylococcus aureus (called VISA and VRSA for Vancomycin Intermediate/Resistant Staphylococcus aureus) and strains of Enterococcus (Vancomycin-Resistant Enterococcus or VRE) have emerged.
Will I be tested if I am taking oral vancomycin?
Oral vancomycin therapy is rarely monitored as only tiny amounts of the drug are absorbed and carried in the blood. Occasionally, someone with impaired renal function will be monitored to verify that the drug is not building up in their body.
Can I test vancomycin levels at home?
Although someone may receive intravenous vancomycin therapy at home, usually administered by a home health professional, blood levels cannot be monitored at home. The test requires specialized equipment and must be performed in the laboratory. The home health professional may draw a blood sample prior to administering the next dose of drug. This sample will be sent to a laboratory for analysis.
Do some medicines interact badly with vancomycin?
Some drugs do interact with vancomycin. Tell your healthcare practitioner if you are taking any other medicines, especially aminoglycosides, amphotericin B, bacitracin, cisplatin, colistin, polymyxin B, or viomycin. These drugs may increase risk of side effects including kidney toxicity or hearing loss.