Indication

• Infections due to gram-positive bacteria including septicaemia.

Postconceptional age = gestational + postnatal age

Supply

• Vancomycin 500mg vial containing powder for reconstitution.

Preparation

• Add 9·7mL (Hospira and Wockhardt brands) of water for injections to 500mg vial resulting in a 50mg/mL concentration.
• For other brands, refer to local displacement value table, or Injectable Medicines Guide https://medusa.wales.nhs.uk/Home.asp. (The Injectable Medicines Guide is also available under the Clinical Applications tab on the NHS Highland intranet).
• Take 1mL of the 50mg/mL solution and dilute to 10mL with sodium chloride 0·9% or glucose 5% resulting in a final concentration of 5mg/mL.

Monitoring

• Monitor renal function.

Therapeutic Drug Monitoring

Trough levels (pre-dose) should be done 24 hours after starting vancomycin and after changing dose ie:

• Trough level should be 10 to 20mg/L.
• Peak levels are not normally required.
• If no change in dosage regimen or renal function, repeat trough levels every 4 days.
• If trough is less than 10mg/L:
  • The dosage interval could be shortened, eg, from 12 hourly to 8 hourly
  • OR the dose could be increased proportionately to achieve therapeutic levels. Eg, if the trough needs to increase by 25% to be in the therapeutic range, increase the dose by 25%.
• Repeat the trough level 24 hours after changing the dose.

If trough is greater than 20mg/L:

• Withhold the next dose and recheck the level:
  • 24 hours later for gestational age 28 weeks or less
  • 12 hours later for gestational age 29 to 35 weeks
  • 8 hours later for gestational age 36 weeks +
• Consider increasing dosing interval, eg, from 8 hours to 12 hours.

If the trough level is greater than 25mg/L:

• Recheck the trough when the next dose is due, ie, 8, 12 or 24 hours.

Seek advice on dose from Pharmacy if required.

If renal function is impaired, eg a change in creatinine of more than 15 to 20%:

• Check the trough level and know the result before the next dose is administered.
• 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?
  • Has renal function declined or improved?
  • Does the patient have oedema or ascites?

If in doubt, take another sample before modifying the dosage regimen and/or contact pharmacy for advice.