Adjusting the vancomycin dosage in adults based on the trough plasma concentration

When using the vancomycin trough plasma concentration to guide dosing, consider if the timing of the sample was appropriate (ie taken within the 60 minutes predose), and whether steady state has been achieved (which depends on kidney function; see timing of trough samples in Recommended timing of vancomycin trough concentration sample and target trough ranges in adults). Suggested dosage adjustment to achieve a target of 10 to 15 mg/L in adults receiving intermittent vancomycin infusions is included in Adjusting the vancomycin dosage in adults receiving intermittent dosing based on trough concentration.

If the vancomycin plasma trough concentration is far outside the expected target range and sampling conditions were not optimal, consider:

  • taking another sample and repeating the measurement
  • using Bayesian dosing software to aid interpretation and to determine subsequent management.

Dose adjustments should be made in a linear manner – a worked example calculation of linear dose adjustment for vancomycin in an adult is given in Adjusting the vancomycin dosage in adults receiving intermittent dosing based on trough concentration. If an intermittent dose of more than 2 g is required to achieve the trough target range, seek expert advice; it may be preferable to increase the dosing frequency (ie change from twice daily to 3- times daily).

Table 1. Adjusting the vancomycin dosage in adults receiving intermittent dosing based on trough concentration[NB1] [NB2]

Trough plasma concentration [NB3]

Suggested dosage adjustment to achieve a target of 10 to 15 mg/L

less than 10 mg/L

increase the dose [NB4]

10 to 15 mg/L

maintain current dosage [NB5]

16 to 20 mg/L

reduce dose [NB4] [NB5]

monitor for nephrotoxicity

more than 20 mg/L

withhold the dose until concentration is less than 15 mg/L and seek expert advice

Note:

NB1: The recommendations in this table do not apply to patients with central nervous system infection. See Vancomycin monitoring in adults with a central nervous system infection or seek expert advice.

NB2: Area under the concentration–time curve over a 24-hour period (AUC24) monitoring is preferred in all patients; if possible, transition to AUC24-based monitoring.

NB3: The recommendations in this table assume the timing of the trough sample was appropriate (ie predose) and steady state has been reached.

NB4: Dosage adjustments should be made in a linear manner – a worked example calculation of linear dose adjustment for vancomycin in an adult is given in Adjusting the vancomycin dosage in adults receiving intermittent dosing based on trough concentration.

NB5: In patients who are critically ill or unstable, patients with severe, necrotising or deep-seated infections, or patients with suspected or confirmed Staphylococcus aureus bacteraemia, AUC24 monitoring should be used; however, if this is not possible, a trough concentration at the upper end of the trough target range may be preferred to more predictably achieve an AUC24 of 400 to 600 mg.hr/L.

Table 2. Example calculation of linear dose adjustment in an adult receiving a vancomycin intermittent infusion

A 50 kg patient with creatinine clearance of 70 mL/minute is receiving a vancomycin intermittent infusion of 750 mg 12-hourly. The vancomycin target trough plasma concentration for this patient is 15 mg/L. The patient’s actual trough plasma concentration is 8 mg/L.

adjusted infusion dose (g)

= target trough vancomycin plasma concentration (mg/L) ÷ actual trough plasma concentration (mg/L) × current dose (g)

= 15 mg/L ÷ 8 mg/L × 0.750 g

= 1.4 g 12-hourly (without rounding) [NB1]

= 1.5 g 12-hourly (with rounding)

Note:

NB1: The final vancomycin dosage should be rounded up to the nearest 125 mg.