title: Determination of allopurinol and oxypurinol in human plasma and urine by liquid chromatography-tandem mass spectrometry.
abstract: Allopurinol is used widely for the treatment of gout, but its pharmacokinetics is complex and some patients show hypersensitivity, necessitating careful monitoring and improved detection methods. In this study, a sensitive and reliable liquid chromatography-tandem mass spectrometry method was developed to determine the concentrations of allopurinol and its active metabolite oxypurinol in human plasma and urine using 2,6-dichloropurine as the internal standard (IS). Analytes and the IS were extracted from 0.5ml aliquots of plasma or urine using ethyl acetate and separated on an Agilent Eclipse Plus C18 column using methanol and ammonium formate-formic acid buffer containing 5mM ammonium formate and 0.1% formic acid (95:5, v/v) as the mobile phase (A) for allopurinol or methanol plus 5mM ammonium formate aqueous solution (95:5, v/v) as the mobile phase (B) for oxypurinol. Allopurinol was detected in positive ion mode and the analysis time was about 7min. The calibration curve was linear from 0.05 to 5μg/mL allopurinol in plasma and 0.5-30μg/mL in urine. The lower limit of quantification (LLOQ) was 0.05μg/mL in plasma and 0.5μg/mL in urine. The intra- and inter-day precision and relative errors of quality control (QC) samples were ≤11.1% for plasma and ≤ 8.7% for urine. Oxypurinol was detected in negative mode with an analysis time of about 4min. The calibration curve was linear from 0.05 to 5μg/mL in plasma (LLOQ, 0.05μg/mL) and from 1 to 50μg/mL in urine (LLOQ, 1μg/mL). The intra- and inter-day precision and relative errors were ≤7.0% for plasma and ≤9.6% for urine. This method was then successfully applied to investigate the pharmacokinetics of allopurinol and oxypurinol in humans.
authors.affiliation: Department of Pharmacy, Guangzhou Brain Hospital, Guangzhou Medical University, 36 MingXin Road, Guangzhou 510370, China.
authors.forename: Xia
authors.initials: X
authors.lastname: Liu
authors.forename: Xiao-Jia
authors.initials: XJ
authors.lastname: Ni
authors.forename: De-Wei
authors.initials: DW
authors.lastname: Shang
authors.forename: Ming
authors.initials: M
authors.lastname: Zhang
authors.forename: Jin-Qing
authors.initials: JQ
authors.lastname: Hu
authors.forename: Chang
authors.initials: C
authors.lastname: Qiu
authors.forename: Fu-Tian
authors.initials: FT
authors.lastname: Luo
authors.forename: Yu-Guan
authors.initials: YG
authors.lastname: Wen
mesh_terms: D000493:Allopurinol / Q000097:blood / Q000493:pharmacokinetics* / Q000652:urine; D002138:Calibration; D002853:Chromatography, Liquid / Q000379:methods*; D006074:Gout Suppressants / Q000097:blood / Q000493:pharmacokinetics* / Q000652:urine; D006801:Humans; D057230:Limit of Detection; D010117:Oxypurinol / Q000097:blood / Q000493:pharmacokinetics* / Q000652:urine; D012015:Reference Standards; D015203:Reproducibility of Results; D021241:Spectrometry, Mass, Electrospray Ionization; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: D006074:Gout Suppressants; D000493:Allopurinol; D010117:Oxypurinol
keywords: Allopurinol; HPLC-MS/MS; Human plasma; Metabolite; Pharmacokinetics