Vancomycin

Chemical Pathology

Notes

• Vancomycin levels are performed in the Chemical Pathology Department on the GRH site. Please send requests using a Chemical Pathology request form (not Microbiology) to avoid delays in sample receipt and analysis.
• Vancomycin levels can be taken at any time of day but the collection time should be convenient for the patient and for the testing laboratory
• Most vancomycin levels are planned (non-urgent) investigations - samples should ideally NOT be collected or sent for testing between midnight and 6am, except in exceptional circumstances.
• For requests out of hours please contact the on-call biomedical scientist in Chemical Pathology to inform them that a sample is being sent

When to test

• Only patients on iv vancomycin require monitoring of serum vancomycin levels. On rare occasions it may be necessary to perform vancomycin levels in selected patients receiving high dose oral vancomycin - see Vancomycin Policy for further details.
• Only pre-dose (trough) levels are required.
• For adults not on haemodialysis or haemofiltration, samples should be collected just before the 2nd to 5th dose depending on creatinine clearance.

• For paediatric patients, samples should be collected just before the 4th dose - earlier if there is renal compromise
• Normally levels can be monitored every 2 - 3 days if the initial level was satisfactory and renal function is stable
• If renal function is unstable levels should be monitored daily
• For routine monitoring of pre-dose levels in patients not on haemodialysis or haemofiltration, the patient should continue receiving subsequent dose(s) of vancomycin pending getting the results of the vancomycin levels back. Doses of vancomycin should not be omitted in these circumstances. See Vancomycin Policy for further details.
• The vancomycin regime should be reviewed in the light of the results of the vancomycin level - normally in the interval between when the dose has just been given and when the subsequent vancomycin dose is due.
• When a patient is having a random vancomycin level checked to see if a high previous level has dropped to an acceptable level it is reasonable to withhold further doses of vancomycin until the results of the random vancomycin level are known. Circumstances when vancomycin should be withheld should be discussed with a specialist clinician.
• Different monitoring arrangements are required for the DCC vancomycin regime and for renal patients on haemodialysis or haemofiltration receiving vancomycin. See Vancomycin Policy for further details.

Result interpretation

Target serum vancomycin concentrations (levels) for patients not on haemodialysis or haemofiltration:

• Pre-dose (trough) levels should be 10 - 20 mg/L routinely *
• Post-dose levels are NOT required

* If the patient is seriously ill (severe or deep-seated infections), the target range is 15 - 20mg/L. If the measured concentration is <15mg/L, consider increasing the dose or reducing the dosage interval - see Vancomycin Policy.

• Always check that the dosage history and sampling time are appropriate before interpreting the result
• Seek advice from Pharmacy or Microbiology if you need help to interpret the result

If the measured concentration is unexpectedly HIGH or LOW, consider the following:

• Were the dose and sample times recorded accurately?
• Was the correct dose administered?
• Was the sample taken from the line used to administer the drug?*
• Was the sample taken during drug administration?*
• Was the sample taken post administration (post-dose), inadvertently?*
• Has renal function declined or improved?
• Does the patient have oedema or ascites?

*If any of these are applicable, repeat the pre-dose vancomycin level prior to the next dose to clarify.

If in doubt about the vancomycin levels, repeat the vancomycin level (pre-dose) before modifying the dosage regimen and consider contacting pharmacy for advice.

Target serum vancomycin concentrations (levels) for patients on haemodialysis:

• Pre-dialysis levels should be 15 - 20 mg/L

Target serum vancomycin concentrations (levels) for patients on haemofiltration on DCC:

• Pre-dose levels should be 10 - 20 mg/L

Sample Requirements

Samples must NOT be taken via lines

For Adults

• 5.0 mL of blood taken into a narrow gold top gel tube (or rust top for the Acute Unit)

For Small Children and Neonates

• A minimum of 1 mL of whole blood taken into a plain tube

Storage/transport

Send at ambient temperature to the laboratory. If unavoidable, store refrigerated until transport available.

Required information

Relevant clinical details and information regarding time of sampling, dosing regime and start date of vancomycin must be included on the request form - this information is crucial for result interpretation.

Record the exact time of all vancomycin levels on the sample and request form.

Turnaround time

• The assays are run throughout the day and night.
• The in-lab turnaround time is less than 6 hours.
• Results are made available on the computer as soon as they are technically approved. Additional comments may be added later by the Consultant Microbiologist when results are clinically approved.
• The test can be ordered as an urgent investigation.

Page last updated: 17/06/2019