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%.