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Immunoassays are currently not available in commercial kits for the quantification of valproic acid, vigabatrin, pregabalin, and gabapentin, which also cannot suffer the limitations of interferences of substances with similar structures. Chromatography is a good alternative to immunoassay. In this study, a simple and robust non‐derivatization gas chromatography‐mass spectrometry method for simultaneous determination of the above four drugs in human plasma was developed and validated for therapeutic drug monitoring purposes. This method employed benzoic acid as the internal standard with hydrochloric acid for plasma acidification and ACN for precipitate protein. The supernatant was directly injected into gas chromatography‐mass spectrometry for analysis. Good linearity was obtained with linear correlation coefficients of the four analytes of 0.9988–0.9996. Extraction recoveries of valproic acid, vigabatrin, pregabalin, and gabapentin were respectively in the ranges of 91.3%–94.5%, 90.0%–90.9%, 90.0%–92.1%, and 88.0%–92.2% with the relative standard deviation values less than 12.6%. Intra‐ and inter‐batch precision and accuracy, and stability assays were all acceptable. Taken together, the novel method developed in this study provided easy plasma pretreatment, good extraction yield, and high chromatographic resolution, which has been successfully validated through the quantification of valproic acid in the plasma of 46 patients with epilepsy. [ABSTRACT FROM AUTHOR]

We aim to establish a simple and easy high‐performance liquid chromatography system coupled with an ultraviolet detector suitable for simultaneous determination of 24 antiepileptic drugs in human plasma. Optimized chromatographic separation was performed on a ZORBAX Eclipse Plus‐C18 (4.6 × 150 mm2, 3.5 μm) column with acetonitrile and 5 mM potassium dihydrogen phosphate water solution as mobile phase. Note that, 24 antiepileptic drugs were divided into three groups and eluted with different gradient procedures, respectively. The column temperature was maintained at 35°C and the detection wavelength was set at 210 nm. Plasma was processed with ethyl acetate or acetonitrile. The calibration curves of 24 antiepileptic drugs demonstrated good linearity within the test range (r > 0.996). The intra‐ and inter‐batch precision and accuracy were all less than 15%, while extraction recoveries were in the range of 74.57–90.89% with the relative standard deviation values less than 15%. The validated methods have been successfully applied to determination of some antiepileptic drugs in rat or patient plasma. Those results indicated that the developed methods were simple and easy, and could be suitable for the determination of 24 antiepileptic drugs in plasma just by changing the gradient elution procedures of mobile phase. [ABSTRACT FROM AUTHOR]

Abstract Ginkgo biloba leaves extract (GBE), one of the most widely used traditional Chinese medicines worldwide, can be used for the treatment of diabetes mellitus (DM). However, its biotransformation in liver is not fully known under the state of DM. In this study, an off-line hydrophilic interaction × reversed-phase two-dimensional liquid chromatography (HILIC × RP 2D-LC) system coupled with diode array detection (DAD) and quadrupole time-of-flight mass spectrometry (q/TOF-MS) was established for the qualification and quantification of the biotransformation of GBE in normal and diabetic rat liver microsomes (RLMs). 6 metabolites were tentatively identified according to the exact molecular weights and the characteristic fragment ions provided by q/TOF-MS data. The results of metabolic stability showed that the metabolic ratio of four target compounds including quercetin, genistein, kaempferol and isorhamnetin in diabetic RLMs were significantly enhanced when comparing with normal RLMs. The results of enzyme kinetics showed that compared with normal RLMs, the Michaelis-Menten constant (K m) value of genistein was obvious increased while its maximal velocity (V max) and intrinsic clearance (CL int) values were significantly decreased by diabetic RLMs, and the V max and CL int values of kaempferol and isorhamnetin were notably enhanced while their K m values were markedly reduced. For the half-time (t 1/2) values of four target compounds and the K m , V max and CL int values of quercetin, there were not statistically significant changes between normal and diabetic RLMs. The results suggest that the developed off-line 2D LC-DAD-q/TOF-MS method is an easy and accurate approach for the study of GBE biotransformation in RLMs and may provide the essential data for further pharmacological and clinical studies of GBE. Highlights • The biotransformation of GBE in diabetic rat liver microsomes (RLMs) was first investigated. • An off-line 2D LC-DAD-q/TOF-MS was first developed and optimized for the analysis. • 6 mono-glucuronide conjugation metabolites were tentatively characterized. • The metabolic stability of quercetin, genistein, kaempferol and isorhamnetin in diabetic RLMs was obtained. • The enzyme kinetics of quercetin, genistein, kaempferol and isorhamnetin in diabetic RLMs was first reported. [ABSTRACT FROM AUTHOR]

In this study, two independent and complementary liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods were respectively developed and validated for the determination of edaravone or taurine in rat urine, feces and bile after intravenous administration, using 3-methyl-l- p -tolyl-5-pyrazolone and sulfanilic acid as the internal standards (IS). Edaravone was separated on an Agilent Eclipse Plus C 18 column (100 × 2.1 mm, 3.5 μm) using methanol and water (containing 5 mM ammonium formate and 0.02% formic acid) as mobile phase, while taurine was performed on a Waters Atlantis HILIC Silica column (150 × 2.1 mm, 3 μm) using acetonitrile and water (containing 5 mM ammonium formate and 0.2% formic acid) as mobile phase. The mass analysis was performed in a Triple Quadrupole mass spectrometer via multiple reaction monitoring (MRM) with negative ionization mode. The optimized mass transition ion pairs ( m/z ) for quantification were 173.1→92.2 and 187.2→106.0 for edaravone and its IS, 124.1→80.0 and 172.0→80.0 for taurine and its IS, respectively. The validated methods have been successfully applied to the excretion and metabolism interaction study of edaravone and taurine in rats after independent intravenous administration and co-administration with a single dose. The results demonstrated that there were no significant alternations on the metabolism and cumulative excretion rate of edaravone and taurine, implying that the proposed combination therapy was pharmacologically viable. [ABSTRACT FROM AUTHOR]

An LC- MS/ MS method was developed and validated for the simultaneous quantification of edaravone and taurine in beagle plasma. The plasma sample was deproteinized using acetonitrile containing formic acid. Chromatographic separations were achieved on an Agilent Zorbax SB-Aq (100 × 2.1 mm, 3.5 μm) column, with a gradient of water (containing 0.03% formic acid) and methanol as the mobile phase at a flow rate of 0.3 mL/min. The analyte detection was carried out in multiple reaction monitoring mode and the optimized precursor-to-product transitions of m/ z [M+H]+ 175.1 → 133.0 (edaravone), m/ z [M+H]+ 189.1 → 147.0 (3-methyl-1- p-tolyl-5-pyrazolone, internal standard, IS), m/ z [M-H]− 124.1→80.0 (taurine), and m/ z [M-H]− 172.0 → 80.0 (sulfanilic acid, IS) were employed to quantify edaravone, taurine, and their corresponding ISs, respectively. The LOD and the lower LOQ were 0.01 and 0.05 μg/mL for edaravone and 0.66 and 2 μg/mL for taurine, respectively. The calibration curves of these two analytes demonstrated good linearity ( r ＞ 0.99). All the validation data including the specificity, precision, recovery, and stability conformed to the acceptable requirements. This validated method has successfully been applied in the pharmacokinetic study of edaravone and taurine mixture in beagle dogs. [ABSTRACT FROM AUTHOR]