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In this study, a simple, rapid and sensitive ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method is described for determination of ketoconazole (KTZ) in human plasma samples using carbamazepine as the internal standard (IS). Sample preparation was accomplished through one-step liquid-liquid extraction by ethyl acetate, and chromatographic separation was performed on an Acquity BEH C18 column (2.1 mm×50 mm, 1.7 μm) with gradient profile at a flow of 0.45 mL/min. Mass spectrometric analysis was performed using a QTrap5500 mass spectrometer coupled with an electro-spray ionization (ESI) source in the positive ion mode. The MRM transition of m/z 531.2→489.3 was used to quantify for KTZ. The linearity of this method was found to be within the concentration range of 5-15 000 ng/mL for KTZ in human plasma. Only 1.5 min was needed for an analytical run. The method herein described was superior to previous methods and was successfully applied to the pharmacokinetic study of KTZ in healthy Chinese volunteers after oral administration., (© Georg Thieme Verlag KG Stuttgart · New York.)

Heroin is a highly addictive drug, and heroin abuse is considered to be a serious criminal act. The major metabolite of heroin, morphine, can usually be detected as evidence of heroin abuse. However, it is difficult to determine heroin use when morphine and codeine are both detected, because codeine use will also result in the presence of morphine in urine. Therefore, it is important to distinguish heroin abuse from codeine administration. In this study, urine samples from 21 volunteers with various ingestion patterns of a compound codeine phosphate oral solution were used as negative controls, and urine samples from 89 alleged heroin users were used as positive controls. Urine from single and multiple doses of codeine administration were collected at different time points for a systematic comparison. After protein precipitation, the urine samples were analyzed for the presence of free morphine, free codeine and their metabolites by ultra-performance liquid chromatography-tandem mass spectrometry. The method of percentiles, with median and standard interquartile ranges, was used to describe and analyze the data based on the normality of the distribution. The ratios of concentration of morphine and morphine to codeine were found to be the possible criteria to distinguish heroin users from codeine users in Chinese people.

A rapid, sensitive and specific high performance liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS) method for the quantification of 13-cis-retinoic acid (isotretinoin) in human plasma has been developed. Acitretin was employed as the internal standard (IS). The analytes were chromatographically separated on a Shimadzu Shim-pack VP-ODS C18 column (150 mm × 2.0 mm I.D.) with a mobile phase consisting of acetonitrile and water (90:10, v/v). Detection was performed on a single quadrupole mass spectrometer using an electrospray ionization interface with the selected-ion monitoring (SIM) mode. The method showed excellent linearity (r=0.9989) over the concentration range of 10-1500 ng/mL with good accuracy and precision. The intra- and inter-batch precisions were within 10% relative standard deviation. The recoveries were more than 80%. The validated method was successfully applied to a preliminary bioequivalence study of isotretinoin in 20 Chinese healthy male volunteers., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Background: A pharmacogenomics study of cyclophosphamide in systemic lupus erythematosus patients is being conducted in our laboratory in which the plasma concentrations of cyclophosphamide and its active metabolite 4-hydroxycyclophosphamide should be assayed rapidly and sensitively., Methods: A rapid, stable and sensitive liquid chromato-graphy/electrospray ionization tandem mass spectrometry method was developed to simultaneously determine cyclophosphamide and 4-hydroxycyclophosphamide in human plasma with ifosfomide as an internal standard. After a protein precipitation with cold acetonitrile and stabilization of 4-hydroxycyclophosphamide by ansyldrazine and extraction with ethyl acetate, separation was performed on a C18 3.5 μm 2.1 × 50 mm column with mobile phase of acetonitrile and water (50:50, v/v) with 0.1% formic acid at 200 μL/min. The chromatographic run time was 3 min., Results: The linear calibration curves ranged from 5 to 5000 ng/mL for cyclophosphamide and 5-500 ng/mL for 4-hydroxycyclophosphamide. The recoveries of the liquid extraction were 54.5%-58.5% for cyclophosphamide and 103.5%-105.5% for 4-hydroxycyclophosphamide. The lower limit of quantification was 5 ng/mL for both analytes. The intra- and inter-day precision was <15% for quality control samples at 4000, 500, 50 ng/mL for cyclophosphamide and 4-hydroxycyclophosphamide at 400, 100, 20 ng/mL. The method was applied in this pharmacogenomics study in Chinese systemic lupus erythematosus patients treated with low-dose cyclophosphamide., Conclusions: The method was efficient with shorter running time and lower limit of quantification compared to previous reports and has been successfully applied in this pharmacogenomics study.

A simple, sensitive and rapid LC-MS/MS method has been developed and validated for the identification and quantification of bivalirudin in human plasma using nafarelin as the internal standard. Following protein precipitation with methanol, the analytes were separated on a C(18) column interfaced with a triple-quadrupole tandem mass spectrometer using positive electrospray ionization. Quantification of bivalirudin was conducted by multiple reaction monitoring (MRM) of the transitions of m/z 1091.4-->(356.4+227.4) for bivalirudin and m/z 662.4-->328.5 for IS. The lower limit of quantification was 1.25ng/ml, and the assay exhibited a linear range of 1.25-500ng/ml. The developed assay method was successfully applied to a pharmacokinetic (PK) study in healthy volunteers after intravenous administration of bivalirudin., (Copyright 2009 Elsevier B.V. All rights reserved.)

A sensitive method for measuring sifuvirtide, a novel HIV fusion inhibitor peptide drug in HIV-1(+) human plasma by liquid chromatography-tandem mass spectrometry (LC-MS/MS) was developed. The plasma samples were treated by solvent/detergent (S/D) method to inactivate viral activity before analysis. After protein precipitation sifuvirtide was determined by LC-MS/MS. A structure analog was used as internal standard (IS). The mass spectrometer was operated in positive ion and multiple reaction monitoring mode with transitions m/z 946.3-->159.0 for sifuvirtide and 951.7-->159.2 for IS. The intra-day precision ranged from 2.74% to 7.57% with accuracy from 91.63% to 102.53%. The inter-day precision ranged from 2.65% to 3.58% and the accuracy from 95.53% to 105.28%. Stability studies showed that sifuvirtide was stable both during the assay procedure and long-term storage. The lower limit of quantitation (LLOQ) was 9.75ngml(-1). The method was used for analyzing samples from phase IIa clinical study of sifuvirtide in China., (Copyright 2009 Elsevier B.V. All rights reserved.)

Valone has a chronic and toxic anticoagulant rodenticide that has widely used in China and has resulted in some accidental and intentional intoxication in recent years. The literature reported so far lacks sensitive and selective method for the confirmation of valone. The purpose of this study was to establish a novel assay for the identification and quantification of valone in serum by ion chromatography-electrospray ionization tandem mass spectrometry (IC-MS/MS). After serum sample was extracted with methanol/acetonitrile (10:90, v/v) and cleaned by Oasis HLB solid-phase extraction cartridge, chromatographic separation was performed on an Ionpac AS11 column with an eluent of methanol/30 mmol/L KOH (10:90, v/v). The overall extraction efficiency was >81.0%, and the limit of quantification was 0.5 ng/mL for valone. Regression analysis of the calibration data revealed good correlation (r(2)>0.99) for valone. Intra- and inter-day precisions for quality-control samples were less than 8.0 and 13.7%, respectively. The proposed method enables the identification and quantification of valone in both clinical and forensic specimens.