Antiepileptic drugs (AEDs) are the mainstay of epilepsy treatment. Since 1989, 18 new AEDs have been licensed for clinical use and there are now 27 licensed AEDs in total for the treatment of patients with epilepsy. Furthermore, several AEDs are also used for the management of other medical conditions, e.g., pain and bipolar disorder. This has led to an increasingly widespread application of therapeutic drug monitoring (TDM) of AEDs, making AEDs among the most common medications for which TDM is performed. The aim of this review is to provide an overview of the indications for AED TDM, to provide key information for each individual AED in terms of the drug’s prescribing indications, key pharmacokinetic characteristics, associated drug-drug pharmacokinetic interactions and the value and the intricacies of TDM for each AED. The concept of the reference range is discussed as well as practical issues such as choice of sample types (total vs free concentrations in blood vs saliva) and sample collection and processing.
The present review is based on published articles and searches in PubMed and Google Scholar, last searched March in 2018, in addition to references from relevant papers.
In total, 171 relevant references were identified and used to prepare this review.
TDM provides a pragmatic approach to epilepsy care in that bespoke dose adjustments are undertaken based on drug concentrations so as to optimize clinical outcome. For the older first generation AEDs (carbamazepine, ethosuximide, phenobarbital, phenytoin, primidone and valproic acid), much data has accumulated in this regard. However, this is occurring increasingly for the new AEDs (brivaracetam, eslicarbazepine acetate, felbamate, gabapentin, lacosamide, lamotrigine, levetiracetam, oxcarbazepine, perampanel, piracetam, pregabalin, rufinamide, stiripentol, sulthiame, tiagabine, topiramate, vigabatrin and zonisamide).