Dried blood spots for monitoring and individualization of antiepileptic drug treatment.

Therapeutic drug monitoring (TDM) is a multi-disciplinary clinical specialty used for optimization and individualization of drug therapy in the general and special populations. Since most antiepileptic drugs (AEDs) are characterized by pronounced intra- and inter-individual variability, it can be especially valuable as an aid for dosing adjustments in patients with epilepsy. Dried blood spots (DBS) sampling technique is recognized as a suitable alternative for conventional sampling methods as TDM interventions should be applied in the most cost-effective, rational and clinically useful manner. In the present review we summarize the latest trends and applications of DBS in TDM of epilepsy. Quantification of AEDs in DBS was employed in various clinical settings and has been already reported for phenobarbital, phenytoin, valproic acid, clonazepam, clobazam, carbamazepine, topiramate, rufinamide, lamotrigine, 10-hydroxycarbazepine and levetiracetam. The major limitation of the published studies are restricted evaluation of critical parameters such as the impact of spotted blood volume, spot homogeneity and haematocrit effect, limited clinical validation and non-established correlations between the DBS and plasma concentrations of AEDs. Standardization of critical technical aspects for appropriate sampling, sample preparation and validation of the analytical procedures for quantification of the drugs, as well as appropriate interpretation of the results are the fields which should get more attention in upcoming studies. Limited data on clinical validation and the fact that this technique has been used in practice only for a few AEDs makes the routine implementation of TDM of AEDs using DBS method a big challenge that should be faced by the pharmaceutical scientists in the future.