Evaluation of the Real-World Practice of Model-Informed Therapeutic Drug Monitoring and Its Association With Pharmacokinetic Target Attainment Rates: A Large-Scale, Single-Center Retrospective Study

BACKGROUND: Model-informed therapeutic drug monitoring (TDM) optimizes drug-dosing regimens using concentration measurements and mathematical models. Despite its importance, the implementation of TDM and pharmacokinetic (PK) target attainment rates may vary across drug and clinical settings. This study assessed TDM implementation and PK target attainment rates at Seoul National University Hospital using electronic medical records. METHODS: Patient data for 24 drugs with established in-house concentration tests and at least 1 concentration measurement between January 2015 and December 2023 were extracted from a clinical data warehouse. Clinical covariates, including age, height, weight, and serum creatinine and albumin levels, were matched to the concentration data. Model-informed TDM use was indirectly calculated based on the number of patients and tests with TDM consultation orders because consultations relied entirely on a PK model. A generalized linear mixed-effects model was used to evaluate the association between TDM consultations and PK target attainment rates. RESULTS: A total of 44,474 eligible patients were identified after excluding 7 patients with duplicate records. The proportion of patients receiving TDM consultations varied by drug, with vancomycin (100%), digoxin (70%), and theophylline (59%) having the highest proportions. For most drugs, the PK target attainment rates were significantly higher with TDM consultation, but for carbamazepine and lithium, they were lower. PK target attainment was lower in patients with decreased renal function, a higher body mass index, or older age. CONCLUSIONS: The use of model-informed TDM, measured as the proportion of TDM consultations, varied across drugs and was generally associated with higher PK target attainment rates. Renal impairment, obesity, and advanced age require specific considerations to determine optimal dosing.