What is being tested?
This test measures the concentration of vancomycin in the blood. Vancomycin is an antibiotic that is used to treat serious infections caused by gram-positive bacteria, such as Staphylococcus. 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 antibiotics 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), skin and soft tissue infections, some pneumonias (lung infection) and meningitis. It is often the drug of choice for two types of Staphylococcus infections such as methicillin-resistant Staphylococcus epidermidis and methicillin-resistant Staphylococcus aureus (MRSA) infections.
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 blood circulation because vancomycin taken by mouth is poorly absorbed by the gut. Once in the blood circulation, the antibiotic can be delivered to the site of infection, and the level will rise and fall as it is metabolised by the body.
Oral vancomycin can be prescribed to treat some Clostridium difficile infections (either severe or relapsed infection). This is an infection that occurs in the gastrointestinal tract where absorption into the circulation is not needed.
The effectiveness of vancomycin depends on keeping blood levels at a therapeutic level (minimum effective concentration), for the 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 and the correct level needed can be calculated and dosing levels adjusted according to test results.
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 level in the blood, then it is unlikely that treatment will be effective. The vancomycin test is used to monitor the amount of drug in the blood to ensure that it is adequate but not excessive.
How is it used?
Vancomycin levels are monitored to ensure that the patient is not under dosed which may lead to a poorer outcome. Monitoring is also necessary to reduce the risk of toxicity.
When is it requested?
In patients with normal renal function, a trough level should be measured before the fourth of fifth dose for intermittent dosing.
What does the result mean?
The recommended target trough level is 15 +/- 3 mg/L for intermittent dosing. Sometimes vancomycin is given through a continuous infusion. In this situation the recommended target is 20 +/- 3mg/L.
Is there anything else I should know?
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. This is not an allergic reaction and can be avoided by administration of vancomycin at an appropriate rate.
Kidney function tests such as creatinine and creatinine urine or eGFR may be requested prior to the start of vancomycin therapy and at intervals, or as needed, to evaluate changes in kidney status.
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.
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.
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.
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.
Yes, in particular the following drugs interact and can affect the action of vancomycin: aminoglycosides, amphotericin B, bacitracin, cisplatin, colistin, polymyxin B, or viomycin.
Your doctor will be aware of these interactions.
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