Therapeutic drug monitoring — branching viva

Opening — the vancomycin level on the ward

Examiner: A six-year-old on intravenous vancomycin for a complicated MRSA bacteraemia has a trough back. What is your monitoring target, and when should the level have been drawn? ^[1]

Candidate (model): For serious MRSA infection my target is the 24-hour area under the concentration–time curve over the MIC — an AUC₂₄/MIC of 400 or more — as set by the 2020 ASHP, IDSA, PIDS and SIDP consensus guideline. AUC-guided monitoring, by two timed levels or Bayesian forecasting from a single level, is preferred over a trough-only strategy because it achieves target exposure with less nephrotoxicity. A true trough is drawn within 30 to 60 minutes before the next dose, at steady state — about the fourth dose in an older child — and not during the infusion or from the infusing line. ^[1]