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:

1. Initiating treatment, to provide a baseline steady-state concentration (benchmarking)
2. Adjusting dosage, to confirm new drug concentration for the patient.
3. Establishing an individual therapeutic range once the desired clinical response has been achieved
4. Determining the magnitude of dose increases, particularly with AEDs showing dose-dependent pharmacokinetics.
5. Diagnosing clinical toxicity, to help identify the responsible drug in multi-drug treatments.
6. Seizures persist, despite an apparently adequate dosage.
7. Status is difficult to assess clinically, such as in young children and patients with mental disability.
8. Altered pharmacokinetics is suspected (due to age-related factors, pregnancy, associated disease, or drug–drug interactions), to confirm and adjust dosing
9. Changing drug formulations (including switches involving generic formulations), to assess potential changes in steady state AED concentration.
10. Poor compliance is suspected, to differentiate between lack of compliance and poor absorption, fast metabolism, and drug interactions.
11. An unexpected clinical change occurs