title: Determination of antiepileptic drugs in biological matrices by LC/MS/MS with a focus on their role in forensic cases
Creators: name: Deeb, Shaza
Publisher: name: University of Glasgow
Year: 2016
Subjects: subject: Gabapentin, pregabalin, antiepileptic drugs, drug abuse, LC/MS/MS, urine, hair, whole blood, plasma, serum, therapeutic drug monitoring.

description: Antiepileptic drugs (AEDs) are prescription only medications which were firstly introduced in the 1880s to treat epilepsy. However, the rapid growth in the drug discovery market led to a new generation of AEDs with multiple mechanisms of action. These new drugs represent a promising treatment for many diseases in addition to epilepsy such as neurological disorders, psychological disorders and substance and alcohol abuse treatment as substitutes for benzodiazepines and methadone. However, their multiple roles triggered their misuse potential and concern on their abuse potential was raised in the literature, the media, and by many addiction organizations. Hence, this research highlights some of the AEDs which have raised concern and discusses their therapeutic effects, mechanism of action as well as their overdose and abuse probability from a forensic toxicology point of view. 
Some AEDs have a narrow therapeutic index and require therapeutic drug monitoring in order to attain the optimum response. The majority of published analytical methods focuses on their analysis in serum and plasma within therapeutic ranges and includes a maximum of 11 AEDs in one analytical step. Therefore, a robust and accurate method was developed for the simultaneous analysis of 15 common AEDs and two of their major metabolites in whole blood using LC/MS/MS. The method was validated according to the standard practices for method validation in forensic toxicology (SWGTOX, May 2013) over a wide concentration range to include AED therapeutic and toxic concentrations which make it suitable for both clinical and forensic analysis.
Stability studies are of great importance in forensic cases where it takes up to a few weeks for autopsy, sampling, drug screening and finally confirmation analysis. However, reports specifically addressing the stability of antiepileptic drugs in whole blood are relatively scarce compared with those for drugs of abuse. Thus, using the previous method, the stability of AEDs in whole blood was investigated under different storage conditions.
The LC/MS/MS method developed for AEDs analysis in whole blood was successfully transferred to another laboratory and extended to include 18 AEDs and 4 metabolites. It was revalidated for AEDs analysis in serum and plasma in addition to whole blood. Before any new method can be adapted to routine forensic analysis, it has to be validated using authentic samples. A total of 467 previously processed samples were reanalysed using the transferred method. The results were compared to the reference laboratory's values and these showed a very good correlation.
The prevalence of AED abuse, namely gabapentin and pregabalin, was investigated among prisoners. 904 urine samples were collected from 8 prisons in Scotland over a one month period. Firstly, a simple and accurate method was developed and qualitatively validated for 21 AEDs in urine to screen the urine samples. Secondly, the method was quantitatively validated for the positive AEDs. 
Drug analysis in hair has multiple applications in clinical laboratories and forensic toxicology. However, only a few papers have considered conventional AEDs analysis in hair for therapeutic drug monitoring purposes. As part of this research, AED extraction from hair samples was investigated. Six different digestion methods and 4 clean-up procedures were compared for 16 AEDs. An LC/MS/MS method was qualitatively validated using the extraction procedure that attained the highest recovery with all AEDs. Subsequently, two authentic hair samples were tested and the method was quantitatively validated for the positive AEDs in these samples.