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Background: Perampanel (PER) is a third-generation antiepileptic drug (AED). Several methods have been developed for the quantification of perampanel in plasma. The pharmacokinetic characteristics of perampanel in healthy Chinese ubjects have not been comprehensively reported. Objective: A simple, fast and sensitive LC-MS/MS method was established and validated for the quantification of perampanel in human plasma and its application to a bioequivalence study. Methods: Chromatographic separation was accomplished on a ZORBAX Eclipse XDB-Phenyl column (4.6 mm × 75 mm, 3.5 μm) using a binary gradient with mobile phase (A) (water containing 5 mmol/L ammonium acetate and 0.1% formic acid and (B) acetonitrile-water (95:5, v/v) at a flow rate of 0.9 mL/min and sample preparation was by one-step protein precipitation via acetonitrile. Results: The total run time in this study was 4.5 min and the retention time of perampanel and perampanel-d5 (internal standard) were 2.30 min and 2.32 min, respectively. The method was developed and validated over the concentration range of 2.00-500 ng/mL for perampanel, with a correlation coefficient greater than 0.9992. The inter-day precision was 3.1%-3.8% and accuracy was 98.9%-103.5%. The intra-day precision was 2.4%-6.8% and the accuracy was 97.6%- 104.9%. The extraction recovery ranged from 99.23%-103.84% and the matrix effect was not significant. Perampanel was proved to be stable in solution and human plasma under different tested conditions. The validated method was successfully applied to a randomized, open-label, 2- period, crossover bioequivalence study in healthy Chinese subjects, and the results indicated that bioequivalence was achieved for 2 formulations of the 4-mg perampanel tablet under both fasting and fed conditions, and both treatments were safe and well-tolerated by all study subjects. Conclusion: The validated method was successfully applied to a bioequivalence study of perampanel in human plasma and has achieved satisfactory results.

The bioavailability of clopidogrel bisulfate (CAS 135046-48-9) form I was compared with that of clopidogrel bisulfate form II in 12 male Sprague-Dawley rats. The rats, randomly divided into two groups, received a single oral dose of 8 mg/kg clopidogrel (CP) bisulfate form I and form II, respectively, under fasting condition. The plasma concentrations of CP and its inactive carboxylic acid metabolite (CAS 144457-28-3, IM) were simultaneously determined by a sensitive, specific LC-MS/MS method. The pharmacokinetic parameters included C(max), T(max), t1/2, AUC(0-t), AUC(0-infinity). The AUC(0-infinity) of CP was 13.78 +/- 0.67 and 11.46 +/- 1.98 ng/ mL x h for CP form I and form II, respectively. The AUC(0-infinity) of IM was 33.08 +/- 5.76 and 21.67 +/- 8.95 microg/mL x h for CP form I and form II, respectively. The maximum plasma concentration (C(max)) of CP was 3.81 +/- 0.54 ng/mL for CP form I and 3.18 +/- 0.31 ng/mL for CP form II, the C(max) of IM was 3.42 +/- 0.41 and 2.08 +/- 0.68 microg/ mL for the CP form I and form II, respectively. There was an obvious difference between form I and form II for C(max) and the area under the plasma concentration time curve for both CP and IM after a t-test. This study shows that CP form I has better bioavailability in rats than CP form II.

A reliable and sensitive liquid chromatographic–tandem mass spectrometric method, with rutin as internal standard, has been developed and validated for simultaneous determination of danshensu, salvianolic acid B (SAB), and hydroxysafflor yellow A (HSYA) in beagle dog plasma. Plasma samples spiked with the analytes were extracted by solid-phase extraction and the analytes were separated on a 250 × 4.6 mm i.d., 5-μm particle, C18 column with methanol–acetonitrile–0.5% formic acid 20:25:55 (v/v) as mobile phase at a flow rate of 1 mL min−1. LC–MS–MS analysis was performed with a Finnigan TSQ triple-quadrupole tandem mass spectrometer operated in negative-ion selected-reaction-monitoring mode, using electrospray ionization. The accuracy and precision of the method were acceptable and linearity was good over the range 20–4,000 ng mL−1 for danshensu, 50–10,000 ng mL−1 for SAB, and 10–2,000 ng mL−1 for HSYA. The method was successfully applied to a pharmacokinetic study of a traditional Chinese medicinal preparation, Danhong lyophilized powder for injection.

To study the NMR phenomena of cetirizine hydrochloride and assign all proton and carbon signals in NMR spectra.To record the 1D and 2D NMR spectra of cetirizine hydrochloride while changing the experimental temperature and adding D2O into the solution.More than one NMR signal or broad peak resulting from piperazine and the attached groups with N atom were given in DMSO-d6 solution at room temperature. "Coalescence" or narrowing had occurred for the proton and carbon signals when the experimental temperature was increased or D2O was added into the solution.Compared with the NMR "time scale", there are more than one conformation of cetirizine hydrochloride in DMSO-d6 solution at room temperature. The different conformation will be exchanged fast while temperature rise and the stable conformation will be existed while D2O was added into the solution.