Consensus Guidelines for Therapeutic Drug Monitoring in Neuropsychopharmacology: Update 2026 - Pharmacokinetic, pharmacogenetic and clinical aspects.

TDM involves measuring and interpreting drug concentrations in blood plasma or serum to optimize pharmacotherapy. In psychiatry and neurology, TDM is a well-established tool for personalized drug treatments. The AGNP-TDM task force initially published guidelines for best practice TDM in 2004, 2011, and 2017. A fundamental methodological revision has now been carried out on how to determine therapeutic reference ranges and dose-related reference ranges transparently and systematically. In the current edition, 50 experts in neuropsychopharmacology offer a complete update of both ranges for each substance following an evidence-based approach. Various types of data were considered for reference range determination, ranging from meta-analyses to drug concentrations expected under recommended doses. Therapeutic reference ranges are now listed for 160 neuropsychiatric drugs, newly included for 30 drugs and revised for 88 drugs. Expected drug concentrations can be calculated based on a revised formula for 162 drugs. Obligatory TDM (i.e. for dose titration) is strongly recommended for 15 neuropsychiatric drugs and recommended for 39 drugs. TDM is classified as useful for 49 drugs and potentially useful for 62 drugs, indicating that it is recommended in specific clinical situations, such as suspected non-adherence, insufficient clinical response despite recommended doses, relapse during maintenance treatment, and many more. The 2026 update includes practical pharmacogenetic recommendations that are directly relevant to TDM. This work integrates a combination of strategies to guide drug treatments in clinical practice using all available tools. A consistent implementation of TDM and pharmacogenetic recommendations will enhance neuropsychopharmacotherapy, improve patient outcomes, and reduce healthcare costs.