This will cover how AED TDM can be usefully employed to manage patients prescribed polytherapy AEDs and polytherapy with other non-AED drugs. The impact of pathologies such as malnutrition, burns and surgery on AED PK and how these can be managed by TDM will also be discussed.
At the end of this session the participants will be able to:
- To understand the importance of antiepileptic drug (AED) interactions in the management of patients with epilepsy.
- To learn how TDM can be used to manage AED pharmacokinetic interactions.
- To learn how concurrent pathologies impact on AED TDM.
The mainstay of epilepsy treatment involves antiepileptic drugs (AEDs). Monotherapy AED treatment typically results in approximately 60-70% of newly diagnosed patients having their seizures controlled effectively whilst switching to an alternative AED monotherapy will result in effective seizure control in 50% of the remaining 30-40% of patients. For the remaining patients, polytherapy AEDs are prescribed in an attempt to control their seizures more effectively. However, these patients can experience problematic adverse pharmacokinetic and pharmacodynamic interactions and these interactions can be exacerbated by concomitant drugs that may be used to treat concomitant or intercurrent comorbidities. As a therapeutic class of drugs, the AEDS are associated with more drug interactions than any other drug class and the purpose of this session is to highlight various pharmacokinetic interactions, how they can be identified, characterised and quantified, and how via the use of TDM they can be managed effectively in the clinical setting. Illnesses, including hepatic or renal failure, infections, burns, stroke, cardiac failure, and other conditions can markedly affect the pharmacokinetics of AEDs and AED TDM should be undertaken in these situations. Furthermore, because protein binding due to hypoalbuminemia typically occurs, measurement of unbound drug concentrations is essential for highly protein bound AEDs (e.g. phenytoin, valproate). Although specific guidelines for extent of TDM are not available, the monitoring of serum AED concentrations is valuable in helping the clinician to identify these pharmacokinetic changes and enabling him or her to make dose adjustments whenever appropriate.