Objectives: Apart from irrational polypharmacy, drug-drug interactions (DDIs) and potentially inappropriate medications for elderly patients, there are numerous challenges referring to psychopharmacological treatment in this patient subgroup prescribed psychotropic agents. Specifically, pharmacokinetics and pharmacodynamics essentially differ in elderly patients, complicating medication selection and dosing.

Methods: Pharmacokinetics involves absorption, distribution, metabolism, and elimination of the medication. Elderly patients often present distinct patterns of medication absorption as well as reduced elimination (due to decreased kidney function). DDIs are another major confounder of medication metabolism. This is particularly

common in elderly patients, as one out of two elderly patients with mental disorders receive polypharmacy which in turn requires careful dose adjustment. Medication adherence is an additional challenge in patients with mental disorders, further complicating pharmacotherapy.

Results: We discuss the benefits of therapeutic drug monitoring (TDM), i.e. the regular measuring of drug concentrations in plasma of patients prescribed psychotropic agents. TDM is a valuable personalized treatment tool; specifically, it allows the determination of the minimum effective dosage also improving safety outcomes. Basic TDM principles, such as steady-state, trough levels and therapeutic reference ranges in the context of elderly patients’ pharmacological treatment will be discussed.

Discussion: The use of TDM is of established clinical value in particularly vulnerable patient subgroups such as elderly patients. Summarizing practical recommendations for TDM in clinical routine we aim to enhance its use ultimately enabling an improvement of treatment effectiveness and safety outcomes in elderly patients prescribed psychotropic agents.