Therapeutic Drug Monitoring: Impact on Efficacy and Safety in Narrow Therapeutic Index Drug Management

By keeping medication concentrations within a specific therapeutic window, Therapeutic Medication Monitoring (TDM), a crucial part of precision medicine, guarantees the best possible therapeutic results. It is essential for the management of medications with a Narrow Therapeutic Index (NTI), in which even little variations in plasma levels can have serious toxicity or subtherapeutic effects. The research analyzed PubMed alongside Scopus and Web of Science databases for articles between 2000 and 2025 under keywords that included "Therapeutic drug monitoring, Narrow therapeutic index drugs, Pharmacokinetic-pharmacodynamic modelling, Model informed precision dosing." Through the integration of pharmacokinetic, pharmacodynamic, and pharmacogenomic data, TDM enables customized dosage to maximize effectiveness and reduce unfavorable drug effects. Because of their limited safety margins and interindividual variability, NTI medications such phenytoin, digoxin, lithium, tacrolimus, and aminoglycosides necessitate cautious dose titration and frequent monitoring. Accurate drug quantification is supported by sophisticated analytical methods such as immunoassays, Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS), and High-Performance Liquid Chromatography (HPLC). Real-time decision-making and customized treatment have been further reinforced by recent advancements like Point-of-Care Testing (POCT), Model-Informed Precision Dosing (MIPD), and artificial intelligence-driven algorithms. Combining TDM with wearable sensor technology and pharmacogenomics opens up new possibilities for ongoing monitoring and enhanced patient safety. Clinical pharmacists are essential in analyzing TDM data, spotting drug-related issues, and directing the right course of treatment. All things considered, TDM is essential to the safe and efficient administration of NTI medications, guaranteeing therapeutic accuracy, reducing toxicity, and encouraging individualized pharmacotherapy for a range of patient demographics.