TDM for Epilepsy & Pain Management
“Measuring serum concentrations of old and new generation antiepileptic drugs (AEDs) can have a valuable role in guiding patient management,” according to Antiepileptic drugs—Best Practice Guidelines for Therapeutic Drug Monitoring, (ILAE 2008). Drug concentrations should be measured with a clear indication and interpreted critically, taking into account the entire clinical context.
For AED therapy, TDM can be indicated when:
- Initiating treatment, to provide a baseline steady-state concentration (benchmarking)
- Adjusting dosage, to confirm new drug concentration for the patient.
- Establishing an individual therapeutic range once the desired clinical response has been achieved
- Determining the magnitude of dose increases, particularly with AEDs showing dose-dependent pharmacokinetics.
- Diagnosing clinical toxicity, to help identify the responsible drug in multi-drug treatments.
- Seizures persist, despite an apparently adequate dosage.
- Status is difficult to assess clinically, such as in young children and patients with mental disability.
- Altered pharmacokinetics is suspected (due to age-related factors, pregnancy, associated disease, or drug–drug interactions), to confirm and adjust dosing
- Changing drug formulations (including switches involving generic formulations), to assess potential changes in steady state AED concentration.
- Poor compliance is suspected, to differentiate between lack of compliance and poor absorption, fast metabolism, and drug interactions.
- An unexpected clinical change occurs
Patsalos PN, Berry DJ, Blaise FD, et al. Antiepileptic drugs—best practice guidelines for therapeutic drug monitoring: A position paper by the subcommission on therapeutic drug monitoring, ILAE Commission on Therapeutic Strategies. Epilepsia, 2008 Jul;49(7):1239-1276.