Topic overview

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TDM can support treatment efficacy, help prevent toxicity, identify possible adherence problems, and account for differences in how patients handle medicines. It is most useful for selected drugs, including aminoglycosides, vancomycin, digoxin, lithium, phenytoin, and certain immunosuppressants; it is not routinely useful for many other drug groups. Reliable interpretation depends on appropriate sample timing, the correct specimen, and accurate documentation of the last dose and sample collection. Results must be considered with the drug’s therapeutic range, patient status, and factors such as organ function, interactions, and critical illness. Drug-specific approaches differ: for example, aminoglycoside peaks and troughs have distinct purposes, while immunosuppressant trough measurements require consistent timing and assay methods.