Rapid Quantification of Gabapentin, Pregabalin, and Vigabatrin in Human Serum by Ultraperformance Liquid Chromatography With Mass-Spectrometric Detection

Green Bio-Analytical Study of Gabapentin in Human Plasma Coupled with Pharmacokinetic and Bioequivalence Assessment Using UPLC-MS/MS

Gabapentin (GAB) is a cyclohexane acetic acid, structurally related to the neurotransmitter gamma-aminobutyric acid (GABA), and considered the principal inhibitory neurotransmitter in the central nervous system (CNS) of mammals. An ultra-performance liquid chromatography–tandem mass spectrophotometry (UPLC-MS/MS) method for assessing pregabalin (PRE) in human plasma, was developed and validated, via PRE usage as an internal standard. The plasma underwent protein precipitation using methanol, prior to analysis. Chromatographic separation was completed using a mobile phase of methanol: 0.1% formic acid solution, (65:35, v/v), at a flow rate of 0.2 mL/min, with an isocratic approach, on an Agilent Eclipse plus column (50 × 2.1 mm and 1.8 μm), in 1.6 min of running time. An Agilent triple quadrupole was used for mass analysis, to detect the ion transitions for GAB and PER, respectively, at m/z of 172.1 → 154.1 and 160.10 → 142.10. The calibration curve, over the linear range of 0.050–10.0 μg/mL, showed a high correlation coefficient, r = 0.9993. The limits of detection and quantitation were 13.37 ng/mL and 40.52 ng/mL, respectively, based on the standard deviation and slope equation. The results for intra- and inter-day measurement accuracy and precision were in acceptable ranges. The method was extended into the assessment of oral administrations of GAB at different doses, of one 600 mg/tablet and two capsules (each one of them has 300 mg of GAB), to volunteers who were used in pharmacokinetics and bioequivalent studies. The AGREE assessment tool was used to visualize the proposed method’s greenness degree, which revealed a high AGREE rating score, supporting the accepted method’s greenness profile.

Green HPLC-DAD and HPTLC Methods for Quantitative Determination of Binary Mixture of Pregabalin and Amitriptyline Used for Neuropathic Pain Management

First analytical methods were herein developed for determination of pregabalin (PGB) and amitriptyline (AMT) as an active binary mixture used for management of neuropathic pain whether in pure forms or in human biological fluids (plasma/urine). First method is green high-performance liquid chromatography-diode array detector (HPLC-DAD) after derivatization of PGB with ninhydrin (NIN) on a reversed-phase C18 column using a mobile phase consisting of ethanol:water (97:3%, v/v) pumped isocratically at 0.8 mL/min; AMT were scanned at 215 nm, whereas PGB-NIN was scanned at 580 nm. Second method is High-performance thin-layer chromatography (HPTLC), where PGB and AMT were separated on silica gel HPTLC F254 plates, using ethanol:ethyl acetate:acetone:ammonia solution (8:2:1:0.05, by volume) as a developing system. AMT peaks were scanned at 220 nm, whereas PGB peaks were visualized by spraying 3% (w/v) ethanolic NIN solution and scanning at 550 nm. Linear calibration curves were obtained for human plasma and urine spiked with PGB and AMT over the ranges of 5-100 μg/mL and 0.2-2.5 μg/band for PGB, and 1-100 μg/mL and 0.1-2.0 μg/band for AMT for HPLC-DAD and HPTLC methods, respectively. The suggested methods were validated according to Food and Drug Administration guidelines for bioanalytical methods validation and they can be applied for routine therapeutic drug monitoring for the concerned drugs.

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.

ESI–LC–MS/MS for Therapeutic Drug Monitoring of Binary Mixture of Pregabalin and Tramadol: Human Plasma and Urine Applications

Tramadol (TRM) and pregabalin (PGB) are frequently used in combination for neuropathic pain management. Accordingly, a selective and sensitive high-performance liquid chromatography–electrospray ionization–mass/mass spectrometric (ESI–LC–MS/MS) method is presented for determination of TRM and PGB, whether in pure forms or human biological fluids (plasma/urine), using gabapentin (GBP) (IS) as the internal standard. Chromatographic separation was effected in total run time of 2.5 min, on Phenomenex Luna® Omega 1.6 um polar C18 (LC 150 × 2.1 mm) column with a mobile phase of methanol/water (70:30, v/v), 0.1% (v/v) formic acid at a flow rate of 0.3 mL/min. Ionization of the analytes was obtained using electrospray in the positive ion mode (ESI+). The MS/MS detection was performed by monitoring the fragments for TRM, PGB and GBP on a triple quadrupole mass spectrometer. Assay calibration was over the range of 10–1000 ng mL−1 for TRM and PGB with the correlation coefficients over 0.999 in pure form, human plasma and urine spiked with the studied compounds. Validation data showed the inter-run relative standard deviations (RSDs) were less than 4.3% for TRM and 3.8% for PGB, whereas the intra-run RSDs were less than 3.7% for TRM and 3.6% for PGB. The mean extraction recoveries for TRM and PGB were in the ranges of 86.51–93.38% and 86.20–92.42%. This method was successfully performed on real plasma and urine samples taken from neuropathic patients and proved to be an applicable method for routine therapeutic drug monitoring of the proposed drug combination.

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.

A Critical Review on Analytical Methods for Recently Approved FDC Drugs: Pregabalin and Etoricoxib

Fixed-dose combinations (FDCs) refer to products containing two or more active ingredients combined in a single dosage form. The FDCs are justified because of several advantages. These are a) potentiating therapeutic efficacy, b) reducing the incidences of adverse drug effects, c) having pharmacokinetic advantages, d) reducing pills burden, e) reducing the dose of individual drugs and f) decreasing the drug resistance development. A recently approved FDC of Pregabalin IP (75 mg) and Etoricoxib (60 mg) recommended to control neuropathic chronic back pain. Analytical methods are available for individual quantitation of pregabalin (PGB) and etoricoxib (ETC), but an effective and reliable analytical method has not been reported for their combination. Thus, the objective of this literature survey was to gather information on various analytical instrumental methods used so far for the individual quantitation of PGB and ETC in various matrices. Such data would be useful to the scientific community to develop a novel analytical method for the analysis of recently approved FDC of PGB and ETC. Various scientific databases were explored to meet the objectives, and the information is synchronized. The reported methods are high-performance liquid chromatography (48% & 53%), hyphenated techniques (54% & 21%), spectroscopy (50% & 34%), and high-performance thin-layer chromatography, or thin-layer chromatography (6% & 13%) for pregabalin and etoricoxib, respectively. All these methods were specific and selective for the analysis of individual drugs.

Ecologically evaluated and FDA-validated HPTLC method for assay of pregabalin and tramadol in human biological fluids

The introduced research presents a novel in vivo quantitative method for assay of mixtures of pregabalin and tramadol as a common combinations approved for treatment of neuropathic pain. Green analytical chemistry is a recently emerging science concerned with control of the use of chemicals harmful to the environment in various analytical methods. Consequently, a green high-performance thin layer chromatography (HPTLC) method was achieved for determination of the mixture in human plasma and urine satisfying both analytical and environmental standards. The separation was achieved on HPTLC sheets using a separating mixture of ethanol-ethyl acetate-acetone-ammonia solution (8:2:1:0.05, by volume) as a mobile phase. The sheets were dried in air then scanned at two wavelengths. For tramadol, 220 nm was chosen; however, pregabalin is an unconjugated drug, so its determination was a challenge. Hence for pregabalin, the plates were sprayed with ethanolic solution of ninhydrin (3%, w/v), to obtain a conjugated complex, which could be assessed at 550 nm. Furthermore, the developed method fulfilled the US Food and Drug Administration validation guidelines, and proved to be useful in therapeutic drug monitoring of this combination. The Eco-scale assessment protocol was implemented to determine the greenness profile of the applied method.

Establishment and Validation of a Sensitive Method for the Detection of Pregabalin in Pharmacological Formulation by GC/MS Spectrometry

Background:

A gas chromatography and mass spectrometry (GC/MS) procedure was developed and validated for the evaluation and quantification of pregabalin (PGN) in pharmaceutical preparations. </P><P> Introduction: Pregabalin is a γ-amino-n-butyric acid derivative used as an antiepileptic drug for the management of fibromyalgia, and has analgesic, anxiolytic, and anticonvulsant activities. Few studies have been reported on the determination of PGN content in pharmaceutical preparations involving gas chromatography - mass spectroscopy.

Methods:

Pregabalin was extracted with MSTFA/NH4F/β- mercapto-ethanol at 60°C for 30 min. The acquired derived molecule of pregabalin was identified by specific ion monitoring mode applying the analytical ions m/z 232 and 331. Propranolol was used as Internal Standard (IS). The following validation parameters were taken into consideration: precision, linearity, accuracy, stability, specificity, robustness, ruggedness, Limit Of Detection (LOD) and Limit Of Quantitation (LOQ).

Results:

The method was selective, precise, sensitive, linear and specific. The linearity of the method was between 3.5 and 300 ng/ml. The precise values were ≤ 3.62% of both intra- and interday validation. The LOD accurate values for Intraday and interday validation were in the range of -0. 25 -2.05%. While LOQ accurate values for intraday and interday were 1.5x10-6 and 3.5 x10-6mg/ml, respectively.

Conclusion:

Therefore, the developed GC-MS method was effectively implemented to identify PGN in a pharmacological preparation.

Development and Validation of an Ultra-Performance Liquid Chromatography-Tandem Mass Spectrometry Method for the Concurrent Measurement of Gabapentin, Lamotrigine, Levetiracetam, Monohydroxy Derivative of Oxcarbazepine, and Zonisamide Concentrations in Serum in a Clinical Setting

BACKGROUND

Therapeutic drug monitoring of antiepileptic drugs (AEDs) is often necessary to prevent associated destructive toxicities. Tandem mass spectrometry (MS/MS) with stable-isotope-labeled internal standards is considered the gold standard for the measurement of AEDs. This study presents the development and validation of a clinical ultra-performance liquid chromatography-MS/MS method for the concurrent measurement of gabapentin, lamotrigine, levetiracetam, monohydroxy derivative of oxcarbazepine, and zonisamide in human serum.

METHODS

To determine the optimal assay analyte range, one year of AED therapeutic drug monitoring results (n = 1825) were evaluated. Simple protein precipitation with acetonitrile containing isotopically labeled internal standards was used. Reverse-phase ultra-performance liquid chromatography chromatographic separation was used, having a total run time of 3 minutes. Quantification of analytes was accomplished using electrospray ionization in positive ion mode and collision-induced dissociation MS. Assay parameters were evaluated per Food and Drug Administration bioanalytical guidelines.

RESULTS

After evaluating internal patient data, the analytical measuring range (AMR) of the assay was established as 0.1-100 mcg/mL. All AEDs were linear across the AMR, with R values ranging from 0.9988 to 0.9999. Imprecision (% coefficient of variation) and inaccuracy (% difference) were calculated to be <20% for the lower limit of quantitation and <15% for the low, mid, and high levels of quality controls across the AMR. All AEDs demonstrated acceptable assay parameters for carryover, stability under relevant storage conditions, matrix effects, recovery, and extraction and processing efficiency. In addition, the assay displayed acceptable concordance to results obtained from a national reference laboratory, with Deming regression R of 0.99 and slope values ranging from 0.89 to 1.17.

CONCLUSIONS

A simple, cost-effective, and robust ultra-performance liquid chromatography-tandem mass spectrometry method for monitoring multiple AEDs was developed and validated to address the clinical needs of patients at our institution.

Development of a Micellar Electrokinetic Chromatographic Method with Indirect UV Detection for Pregabalin Determination in Serum Samples

Background: A micellar electrokinetic chromatographic (MEKC)/ indirect UV detection method with hydrodynamic and electrokinetic injection has been developed for the determination of pregabalin in the serum samples. Methods: Separation of the drug was achieved on Agilent capillary electrophorese in less than 5 min using a 50 cm × 75 μm i.d. uncoated fused-silica capillary and a background electrolyte (BGE) consisting of 5-aminosalicylic acid (5-ASA, 10 mmol L-1), cetyl trimethylammonium bromide (CTAB, 1 mmol L-1) and tri-sodium citrate (4% w/v). The influence of various parameters on the separation such as separation voltage, injection time, cassette temperature, pH of BGE and organic modifier was investigated. Results: Method validation shown good linearity (R2> 0.999) in the range of 1.5-100 µg mL-1 of pregabalin. A limit of detection (LOD) of 0.8 μg mL-1 and a limit of quantitation (LOQ) of 2.6 μg mL-1 were reported for pregabalin. Conclusion: The proposed method was found to be suitable and accurate for the determination of pregabalin in serum samples.

A Validated Fluorometric Method for the Rapid Determination of Pregabalin in Human Plasma Applied to Patients With Pain

BACKGROUND

Pregabalin has been used for the treatment of pain. A clinically accepted method applied to patients with pain has not been published for the determination of pregabalin in human plasma. This study developed a fluorometric ultrahigh-performance liquid chromatography (UHPLC) method to measure pregabalin concentration in patients with pain.

METHODS

After plasma pretreatment involving protein precipitation, pregabalin and gabapentin as an internal standard were derivatized with 4-fluoro-7-nitrobenzofurazan (NBD-F) under the following reaction conditions: 1 minute, pH 10, and 60°C. The UHPLC separation was performed using a 2.3-μm particle size octadecylsilyl column. The fluorescence detector was set at excitation and emission wavelengths of 470 and 530 nm, respectively. The predose blood samples were collected from 40 patients with pain who have been treated with 75 mg of pregabalin twice daily.

RESULTS

The chromatographic run time was 1.25 minutes. No interfering peaks were observed in the blank plasma at the retention times of NBD derivatives. The calibration curve of pregabalin was linear at a range of 0.05-10 mcg/mL (r > 0.999). The lower limit of quantification was 0.05 mcg/mL. The intra-assay accuracy and precision were 98.3%-99.8% and within 4.3%, respectively. The inter-assay accuracy and precision were 103.2%-107.1% and within 4.1%, respectively. The predose plasma concentration of pregabalin in patients with pain ranged from 0.14 to 8.5 mcg/mL.

CONCLUSIONS

This study provides a validated fluorometric UHPLC method with fast analytical performance for the determination of pregabalin in human plasma. The present method could be applied to patients with pain and be used for the clinical research or therapeutic drug monitoring of pregabalin.

Spectroscopic Methods for Quantifying Gabapentin: Framing the Methods without Derivatization and Application to Different Pharmaceutical Formulations

This work aimed at analyzing the performance of direct spectroscopic methods for the quantification of gabapentin (GABAp), given the lack of previous studies, in comparison with the more reviewed and complex derivatization techniques, discussing their susceptibility to the pharmaceutical formulations. All of the methods analyzed showed high selectivity for this pharmaceutical analyte, with recoveries close to 100%. Absorption spectroscopy without derivatization yielded better sensitivity and lower limits of detection and quantification of gabapentin in aqueous solution (AqSol method) when compared with other solvents, such as acidic solution or ethanol/water mixture. Derivatization with sodium hypochlorite presented the highest precision, whereas derivatization with vanillin exhibited the highest accuracy. The best method for GABAp quantification in terms of highest sensitivity, lowest limits of detection, and quantification, and also with good precision and accuracy, proved to be fluorescence with derivatization by 4-chloro-7-nitrobenzofurazan. The effect of the pharmaceutical formulation (nature of excipients) was tested for the most robust and sensitive methods, with and without derivatization, on capsules of five commercial brands. Recoveries in the range of 97.9-101.5% proved that there are no matrix interfering effects. Although not presenting the best performance in all the parameters evaluated, the AqSol method, due to its simplicity, proved to be suitable for the quantification of GABAp in capsules and tables containing the molecule as the active ingredient.

Therapeutic drug monitoring by dried blood spot: progress to date and future directions

This article discusses dried blood spot (DBS) sampling in therapeutic drug monitoring (TDM). The most important advantages of DBS sampling in TDM are the minimally invasive procedure of a finger prick (home sampling), the small volume (children), and the stability of the analyte. Many assays in DBS have been reported in the literature over the previous 5 years. These assays and their analytical techniques are reviewed here. Factors that may influence the accuracy and reproducibility of DBS methods are also discussed. Important issues are the correlation with plasma/serum concentrations and the influence of hematocrit on spot size and recovery. The different substrate materials are considered. DBS sampling can be a valid alternative to conventional venous sampling. However, patient correlation studies are indispensable to prove this. Promising developments are dried plasma spots using membrane and hematocrit correction using the potassium concentration.

Quantification of pregabalin using hydrophilic interaction HPLC-high-resolution MS in postmortem human samples: eighteen case reports

Pregabalin is a drug for treating epilepsy, anxiety disorders and neuropathic pain. Cases of poisoning are rare, though some have been fatal. Concentrations of pregabalin in postmortem human samples and its distribution have very rarely been documented. As the literature is so scarce, we propose to report the concentrations in autopsy samples of 18 people who had been taking Lyrica(®), including one case of a mixed overdose involving pregabalin. Analysis was carried out using an original Hydrophilic Interaction LIquid Chromatography (HILIC) technique coupled with a high-resolution mass spectrometer (m/z 160.1334 ± 5 ppm). The sensitivity of the technique enables a quick and simple treatment of the samples by protein precipitation. The method was validated in the whole blood with detection and quantification limits of 0.025 and 0.060 µg/mL, respectively. Pregabalin was a likely factor in the cause of death in 3 of the 18 cases. In the other individuals, the concentrations ranged from 0.4 to 17.0 in the peripheral blood, 1.5 to 11.1 in the central blood, 126.6 to 2004.6 in the urine and 10.5 to 58.3 µg/mL in the bile, with median values of 5.6, 4.6, 534.6 and 17.7, respectively.