title: Determination of Concentrations of Azathioprine Metabolites 6-Thioguanine and 6-Methylmercaptopurine in Whole Blood With the Use of Liquid Chromatography Combined With Mass Spectrometry.
abstract: BACKGROUND
  6-Mercaptopurine (6-MP) and its prodrug azathioprine (AZA) are used in many autoimmune diseases and after solid-organ transplantation. Their properties are mediated by active metabolites, 6-thioguanine nucleotides (6-TGN), and 6-methylmercaptopurine (6-MMP). The most common adverse effects are myelo- and hepato-toxicity. The aim of the study was quantification of 6-TG and 6-MMP, with the use of liquid chromatography combined with tandem mass spectrometry (LC/MS/MS) in solid-organ transplant recipients.
  
  
  METHODS
  In 33 patients, kidney transplant recipient (n = 25) and liver transplant recipient (n = 8) intra-erythrocyte concentrations of 6-TG and 6-MMP were measured with the use of LC/MS/MS.
  
  
  RESULTS
  The mean concentration of 6-TG was 205.35 ± 157.62 pmol/8 × 10(8) red blood cells (RBC); median concentration of 6-MMP was 1064.1 (35.78-11,552.9) pmol/8 × 10(8) RBC. There were no correlations between 6-TG levels and peripheral blood parameters (white blood cell count, WBC; hemoglobin, Hb concentration; PLT, blood platelet count) or alanine aminotransferase activity (AlAT) activity. Relationships between 6-MMP concentrations and peripheral blood parameters (WBC, Hb, PLT) or AlAT activity have not been found. Subgroups with leukopenia, anemia, thrombocytopenia, and liver dysfunction did not differ in concentrations of 6-TG or 6-MMP. We have observed a negative correlation between daily azathioprine dose and WBC count (r = -0.37, P = .04).
  
  
  CONCLUSIONS
  Relationships between concentrations of azathioprine metabolites and myelotoxicity or hepatotoxicity have not been confirmed. Further studies on larger groups of patients would be helpful in a more accurate understanding of the impact of azathioprine metabolites on parameters of bone marrow and liver function.
authors: Department of Immunology, Transplant Medicine, and Internal Diseases, Medical University of Warsaw, Transplantation Institute, Warsaw, Poland.
authors: D
authors: D
authors: Zochowska
authors: Department of Immunology, Transplant Medicine, and Internal Diseases, Medical University of Warsaw, Transplantation Institute, Warsaw, Poland.
authors: J
authors: J
authors: Zegarska
authors: Department of Clinical Nursing, Medical University of Warsaw, Warsaw, Poland.
authors: E
authors: E
authors: Hryniewiecka
authors: Institute of Biochemistry and Biophysics Polish Academy of Sciences, Warsaw, Poland.
authors: E
authors: E
authors: Samborowska
authors: Institute of Biochemistry and Biophysics Polish Academy of Sciences, Warsaw, Poland.
authors: R
authors: R
authors: Jazwiec
authors: Institute of Biochemistry and Biophysics Polish Academy of Sciences, Warsaw, Poland.
authors: W
authors: W
authors: Tszyrsznic
authors: Institute of Biochemistry and Biophysics Polish Academy of Sciences, Warsaw, Poland.
authors: A
authors: A
authors: Borowiec
authors: Institute of Biochemistry and Biophysics Polish Academy of Sciences, Warsaw, Poland; Department of Biology, University of Warsaw, Warsaw, Poland.
authors: M
authors: M
authors: Dadlez
authors: Department of Immunology, Transplant Medicine, and Internal Diseases, Medical University of Warsaw, Transplantation Institute, Warsaw, Poland. Electronic address: leszek.paczek@wum.edu.pl.
authors: L
authors: L
authors: Paczek
mesh_terms: D000328:Adult; D001379:Azathioprine / Q000009:adverse effects / Q000378:metabolism; D002853:Chromatography, Liquid / Q000379:methods; D004912:Erythrocytes / Q000378:metabolism; D005260:Female; D006150:Guanine Nucleotides / Q000097:blood*; D006801:Humans; D007166:Immunosuppressive Agents / Q000009:adverse effects / Q000378:metabolism; D007958:Leukocyte Count; D008297:Male; D015122:Mercaptopurine / Q000031:analogs & derivatives* / Q000097:blood; D016377:Organ Transplantation; D053719:Tandem Mass Spectrometry / Q000379:methods; D013866:Thioguanine / Q000097:blood*; D013873:Thionucleotides / Q000097:blood*
chemical_list: D006150:Guanine Nucleotides; D007166:Immunosuppressive Agents; D013873:Thionucleotides; C003964:6-thioguanylic acid; C010240:6-methylthiopurine; D015122:Mercaptopurine; D013866:Thioguanine; D001379:Azathioprine