Fluorescent high-performance liquid chromatographic analysis of vigabatrin enantiomers after derivatizing with naproxen acyl chloride

Separation of vigabatrin enantiomers using mixed-mode chromatography and its application to determine the vigabatrin enantiomer levels in rat plasma

Mixed-mode chromatography-comprising a mixed phase with reversed and ionic phases, enabling hydrophobic and ion-exchange interactions simultaneously-was applied to identify vigabatrin enantiomers by HPLC with pre-column fluorescence derivatization with 2,5-dioxopyrrolidin-1-yl (4-(((2-nitrophenyl)sulfonyl)oxy)-6-(3-oxomorpholino)quinoline-2-carbonyl)prolinate (Ns-MOK-(S)-Pro-OSu). The MOK-(S)-Pro-vigabatrin enantiomers were efficiently separated within 12 min (total analysis time per sample: 28 min, including washing and equilibrium time for the column). The mobile phase was H₂O/CH₃OH/10 mM ammonium formate (pH 2.0) (20/20/60, v/v/v). Column temperature was maintained at 60℃. The proposed HPLC method could successfully monitor plasma vigabatrin enantiomer levels in rats administered (±)-vigabatrin (50 mg/kg, p.o.).

Derivatization of γ-Amino Butyric Acid Analogues for Their Determination in the Biological Samples and Pharmaceutical Preparations: A Comprehensive Review

γ-Aminobutyric acid (GABA) plays an important role in regulating neuronal excitability. Four structurally related drugs to GABA including pregabalin (PGB), gabapentin (GBP), vigabatrin (VGB), and baclofen are used for the treatment of central nervous system disorders. These drugs are small aliphatic molecules having neither fluorescent nor strong absorbance in the ultraviolet/visible region; therefore, direct determination of these analytes by optical methods is difficult. Additionally, their high boiling point makes gas chromatography impossible. Accordingly, the amine or acid moiety in these drugs is derivatized in order to improve their selectivity and sensitivity during determination in the biological samples. This review focuses on derivatization based methods and their different reactions for determination of PGB, GBP, VGB, and baclofen in the biological samples and pharmaceutical preparations reported between 1980 and 2020. High-performance liquid chromatography methods coupled with different detectors are a commonly used methods for determination of GABA analogs after derivatization. These methods cover 38.89% of all developed methods for determination of GABA analogs.

Fluorimetric determination of the enantiomers of vigabatrin, an antiepileptic drug, by reversed-phase HPLC with a novel diastereomer derivatization reagent

Herein, determination of an antiepileptic drug, (±)-vigabatrin (VB), was performed by reversed-phase HPLC with fluorimetric detection using a newly designed and synthesized fluorescence derivatization reagent, 2,5-dioxopyrrolidin-1-yl (4-{[(2-nitrophenyl)sulfonyl]oxy}-6-(3-oxomorpholino)quinoline-2-carbonyl)prolinate [Ns-MOK-(R)- or (S)-Pro-OSu]. During the derivatization of VB with Ns-MOK-(R)-Pro-OSu at 60°C, the nosyl (Ns) group, which was introduced to protect a phenolic hydroxy group, was released within 30 min to produce MOK-(R)-Pro-VB, which was detected fluorimetrically at 448 nm with an excitation wavelength of 333 nm. The VB enantiomers were separated on an octadecylsilica (ODS) column with a resolution value of 5.57, because Ns-MOK-(R)-Pro-OSu bears an optically active D-proline structure. A complete separation of MOK-(R)-Pro-(R)- and -(S)-VB enantiomers was achieved on the ODS column within 40 min using stepwise gradient elution, and the detection limits were ~0.80 and 0.37 pmol on the column, respectively. The proposed HPLC with fluorimetric detection method was successfully used for determining VB enantiomers in VB-spiked human serum following solid-phase extraction with an anion-exchange cartridge.

Determination of three antiepileptic drugs in pharmaceutical formulations using microfluidic chips coupled with light-emitting diode induced fluorescence detection

In this study, a facile, sensitive, and precise lab-on-a-chip electrophoretic method coupled with light-emitting diode induced fluorescence (LED-IF) detection was developed to assay three antiepileptic drugs, namely, vigabatrin, pregabalin, and gabapentin, in pharmaceutical formulations. The analytes were derivatised offline for the first time with fluorescine-5-isothiocyanate (FITC) to yield highly fluorescent derivatives with λ_ex/em of 490/520nm. The FITC-labelled analytes were injected, separated, and quantitated by a microfluidic electrophoresis device using fluorescence detection. The labelled analytes were monitored using a blue LED-IF system. The separation conditions were significantly optimised adding specific concentrations of heptakis-(2,6-di-O-methyl)-β-cyclodextrin (HDM-β-CD) and methylcellulose to the buffer solution (40mM borate buffer). HDM-β-CD acted as a selective host for the studied antiepileptic drugs, rendering a high separation efficiency. Methylcellulose was used as an efficient dynamic coating polymer to prevent the labelled drugs from being adsorbed on the inner surfaces of the poly (methylmethacrylate) microchannels. A laboratory-prepared ternary mixture of the three antiepileptic drugs was separated within 100s with acceptable resolution between all the three analytes (R_s>3) and a high number of theoretical plates (N) for each analyte (N≈10⁶ plates/m). The sensitivity of the method was enhanced approximately 80-fold by stacking to yield a detection limit below 0.6ngmL^-1 in the concentration range of 2.0-200.0ngmL^-1. The method was successfully validated for analysing the studied drugs in their pharmaceutical formulations.

Determination of baclofen and vigabatrin by microchip electrophoresis with fluorescence detection: application of field-enhanced sample stacking and dynamic pH junction

A novel microchip gel electrophoretic method for the assay of baclofen and vigabatrin for the first time.

Chiral chromatographic resolution of antiepileptic drugs and their metabolites: a challenge from the optimization to the application

A large number of the antiepileptic drugs (AEDs) presently available for clinical practice are chiral compounds while others, although achiral, may originate pharmacologically active chiral metabolites in vivo. The well-known implications of chirality in pharmacokinetics and pharmacodynamics demand the investigation of pharmacological properties for a racemic mixture and each enantiomer. To achieve these objectives, appropriate chiral analytical methods must be available. This article provides the first review of the current state of the art in chiral chromatographic methods available for quantifying enantiomers of AEDs in distinct matrices. Particular attention is paid to the methodological aspects and optimization strategies that successfully allow enantiomeric chromatographic separation of chiral AEDs and/or metabolites. Furthermore, the relevance of these methods in supporting the discovery and development of chiral AEDs is emphasized. In parallel and whenever available, the principal validation parameters are herein considered and related to the stage of drug discovery and development. In an attempt to optimize anticonvulsant activity and simultaneously diminish toxic effects, many pharmaceutical companies have started to manufacture single enantiomers. Therefore, chiral chromatographic techniques will be essential and the information herein compiled can be used as a framework for developing them.

Modern methods for analysis of antiepileptic drugs in the biological fluids for pharmacokinetics, bioequivalence and therapeutic drug monitoring

Epilepsy is a chronic disease occurring in approximately 1.0% of the world's population. About 30% of the epileptic patients treated with availably antiepileptic drugs (AEDs) continue to have seizures and are considered therapy-resistant or refractory patients. The ultimate goal for the use of AEDs is complete cessation of seizures without side effects. Because of a narrow therapeutic index of AEDs, a complete understanding of its clinical pharmacokinetics is essential for understanding of the pharmacodynamics of these drugs. These drug concentrations in biological fluids serve as surrogate markers and can be used to guide or target drug dosing. Because early studies demonstrated clinical and/or electroencephalographic correlations with serum concentrations of several AEDs, It has been almost 50 years since clinicians started using plasma concentrations of AEDs to optimize pharmacotherapy in patients with epilepsy. Therefore, validated analytical method for concentrations of AEDs in biological fluids is a necessity in order to explore pharmacokinetics, bioequivalence and TDM in various clinical situations. There are hundreds of published articles on the analysis of specific AEDs by a wide variety of analytical methods in biological samples have appears over the past decade. This review intends to provide an updated, concise overview on the modern method development for monitoring AEDs for pharmacokinetic studies, bioequivalence and therapeutic drug monitoring.