therapeutic drug monitoring
Pronunciation: T-D-M
Also written as: TDM — Therapeutic Drug Monitoring
Laboratory measurement of antiepileptic drug levels to optimize dosing and minimize toxicity.
Full Definition
Therapeutic drug monitoring (TDM) involves measuring serum concentrations of antiepileptic drugs (AEDs) to ensure therapeutic efficacy while avoiding toxicity. In pediatric epilepsy, TDM is particularly important due to age-related pharmacokinetic differences, drug interactions, and the narrow therapeutic window of many AEDs. Indications for TDM include suspected non-compliance, breakthrough seizures, signs of toxicity, drug interactions, or significant physiological changes (puberty, illness). The timing of blood draws is crucial - typically obtained at steady state (5 half-lives after dose initiation or change) and as trough levels. Results must be interpreted in clinical context, as therapeutic ranges are population-based and individual patients may require levels outside these ranges for optimal control.
Usage
Usage note: Emphasize clinical correlation; drug levels must be interpreted with symptoms and seizure control, not in isolation.
In Context
- "Therapeutic drug monitoring revealed subtherapeutic phenytoin levels explaining the breakthrough seizures." — Laboratory interpretation
- "TDM was ordered after the patient developed ataxia and diplopia suggesting carbamazepine toxicity." — Clinical assessment