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Vancomycin

Formal name: Vancomycin
Related tests: Therapeutic drug monitoring; creatinine; creatinine clearance

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 drawn 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 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 septicaemia, 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 epidermidis and 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 the 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/her 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.

How is the sample collected for testing?

A blood sample is obtained by inserting a needle into a vein in the arm.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed.

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 are ordered at times to reflect the lowest concentration (trough) and the highest concentration (peak) to evaluate the adequacy of dosing and adequacy of clearance of the drug. 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.

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When is it requested?

There is not a widespread consensus on the use of the vancomycin test. Some doctors 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 on patients who are at increased risk of nephrotoxicity (because of other medications, decreased kidney function, etc.) and on those who are not responding to treatment as expected.

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What does the test result mean?

Looking for reference ranges?

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.

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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 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.

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Common Questions

1.  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 microorganisms. 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 have emerged.

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2.  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 a patient with impaired renal function will be monitored to verify that the drug is not building up in the body.

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3.  Can I test vancomycin levels at home?

Although a patient may receive intravenous vancomycin therapy at home, usually administered by a home health professional, blood levels cannot be monitored at home. The test requires specialised 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.

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4.  Should all antibiotic therapy be monitored like vancomycin?

No, not all antibiotics require monitoring. Unlike vancomycin, most antibiotics have a larger therapeutic range in which they are effective but will not cause side effects. Because of this, they can be prescribed based upon pre-established dosing schedules.

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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.