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Vancomycin Dosing
Last updated 3rd December 2020
Background
- Used for resistant gram pos. bacteria including severe MRSA sepsis, and also for patients with penicillin allergy.
- Like gentamicin, associated with both nephrotoxicity & ototoxicity, risk of which increases with time on drug, high trough levels & concurrent aminoglycosides or loop diuretics
Step 1 Prescribe Loading Dose and Maintenance Dosage Regimen
- Loading dose is based on actual body weight, summarised below and determined using the intranet vancomycin dose calculator
- Infuse in dextrose or saline at rate of 500mg/hr in order to avoid ‘red man’ syndrome (which resolves when infusion rate reduced)
- Dilute doses of up to 1250mg in 250ml 0.9% sodium chloride or dextrose 5%, and doses above 1250mg up to 2000mg in 500ml.
Loading Dose
Maintenance Dosage Regimen
- First dose usually followed by intermittent infusions based on CrCl, though continuous infusions may be preferred on ICU.
- Maintenance dose is based on estimated creatinine clearance (CrCl), summarised below. CrCl is estimated using an internet clearance calculator.
- The daily dose can be split into 3 equal doses and given 8 hourly. This approach is especially useful for patients who require high doses as it produces higher trough concentrations. For example, 1500 mg 12 hourly (3000 mg per day) could be prescribed as 1000 mg 8 hourly and 750 mg 12 hourly (1500 mg per day) as
- 500 mg 8 hourly.
- Note CrCl overestimates actual renal function if oliguria, anuria or AKI – give dose as below then contact microbiologist, pharmacist or nephrologist for advice.
Step 2: Monitor Serum Creatinine and Vancomycin
- Take a trough sample immediately before 3rd dose when using 12 or 24 hour dosing regimens.
- Discuss frequency of serum monitoring with consultant – likely to be daily initially, but may be less frequent thereafter if renal function stable
- Record the exact time of all vancomycin samples on vancomycin prescribing chart and on the sample request form
- Record serum concentration on vancomycin prescription chart , reassessing dose/dose interval as indicated
- If renal function stable give the next dose before trough result available. If renal function deteriorating, withhold until result available then follow advice below
Target Vancomycin Concentrations
- Target trough concentration range 10-20mg/l
- If patient seriously ill (severe or deep seated infection) the target range is 15-20mg/l. If measured concentration <15mg/l consider increasing dose or reducing dose interval
If Serum Vancomycin Unexpectedly High or Low
- Were dose and sample times recorded correctly?
- Was correct dose given?
- Was sample taken from line used to administer the drug?
- Was 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 re-prescribing and/or contact pharmacy for advice
Adjustment of Vancomycin Dosage Regimen
Toxicity
- Risk is mainly that of nephrotoxicity though fortunately this is less than for gentamicin
- Monitor creatinine daily and seek advice if renal function unstable eg change in creatinine >15-20%
- Note that vancomycin may increase risk of gentamicin ototoxicity – seek advice if co-prescribing