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High-performance liquid chromatography (HPLC) coupled with electrospray ionization mass spectrometry (ESI-MS) was applied for the analysis of nabumetone metabolites during the biotransformation in minipigs. In addition to known phase I metabolites, the identification of phase II metabolites was achieved on the basis of their full-scan mass spectra and subsequent MS(n) analysis using both positive-ion and negative-ion ESI mode. Some phase I metabolites are conjugated with both glucuronide acid and glycine, which is quite unusual type of phase II metabolite not presented so far for nabumetone. These metabolites were found in small intestine content, but they were absent in minipigs urine., (Copyright © 2013 Elsevier B.V. All rights reserved.)

A novel T-type calcium channel blocker, 4-amino-1-{4-[(4-chloro-phenyl)-phenyl-methyl]-piperazin-1-yl}-butan-1-one (HYP-10) has been synthesized, and the compound has shown promise as both a nociceptive and inflammatory pain reliever as well as an analgesic in a rat neuropathic pain model. A quantification method was developed for the determination of HYP-10 in rat plasma. After simple protein precipitation with methanol, HYP-10 and the internal standard, methaqualone were chromatographed on a reversed-phase column and detected by liquid chromatography/tandem mass spectrometry with electrospray ionization. The accuracy and precision of the assay were in accordance with FDA regulations for validation of bioanalytical methods. This method was applied to measure the plasma HYP-10 concentration after a single intravenous administration of the compound in rats., (Copyright © 2010 Elsevier B.V. All rights reserved.)

A simple and sensitive high performance liquid chromatography method for the determination of nabumetone in human plasma is described. The procedure involves liquid-liquid extraction with ethyl acetate and reversed-phase chromatography with fluorimetric detection (excitation 230 nm, emission 356 nm). The chromatographic conditions and the extraction procedure gave a clean chromatogram for the compound. The limit of quantitation was established as 0.313 ng/ml and the calibration curve was linear up to 20 ng/ml. The within-day and between-day relative standard deviations were less than 10% and the accuracy of the assay was in the range of 99-104%. The suitability of the method is shown for pharmacokinetic studies.