Methods of estimating vancomycin use in an inpatient setting: days of therapy versus therapeutic drug monitoring-based exposure days.

Underestimating antimicrobial use based on days of therapy (DOT) is recognized for certain antimicrobial agents. We investigated the difference between DOT and therapeutic drug monitoring (TDM)-based exposure days in estimating vancomycin use and demonstrated that DOT may underestimate vancomycin exposure by ∼10%.