Therapeutic Drug Monitoring of Psychotropic Drugs in Inpatient Psychiatry: Local Practice and Improvement

Therapeutic drug monitoring (TDM) is an important tool to personalize psychopharmacotherapy, thereby optimizing its effectiveness and tolerability. Despite consensus on medications, indications, and implementation of TDM, reports indicate a substantial gap between theory and practice. To further investigate this gap, the current application of TDM was assessed in the adult inpatient settings of the University Hospital of Psychiatry and Psychotherapy of Bern, Switzerland.

To assess current practice in TDM, drug level measurements were analyzed in 2022. In parallel, an online survey as well as standardized interviews were conducted with the clinic's physicians. To improve TDM applications, a handout was designed with the core items of the TDM guidelines, revised the orders for TDM in the hospital information system, and held an internal lecture on TDM.

In clinical practice, TDM was primarily used for clozapine, lithium, and valproate. Other drugs appear to be underrepresented. Although physicians generally rated their knowledge of TDM as good, they identified the need for improvement in medical knowledge. The main source of error in TDM was the incorrect timing of blood samples. There was disagreement among the physicians about the number of TDMs.

Therapeutic drug monitoring is well established for clozapine, lithium, and valproate. Compared to the international consensus, physicians applied TDM to a narrower spectrum of psychotropic drugs. Efforts are needed to improve TDM. To optimize TDM, a handout was created, and the TDM request was adapted in the hospital according to guidelines recommendations based on findings of TDM requests, the survey, and interviews.