Determination of Concentrations of Azathioprine Metabolites 6-Thioguanine and 6-Methylmercaptopurine in Whole Blood With the Use of Liquid Chromatography Combined With Mass Spectrometry

• Published in: Transplantation proceedings 2016-06, Vol.48 (5), p.1836-1839
• Main Authors: Zochowska, D, Zegarska, J, Hryniewiecka, E, Samborowska, E, Jazwiec, R, Tszyrsznic, W, Borowiec, A, Dadlez, M, Paczek, L
• Format: Article
• Language: English
• Subjects: Adult; Azathioprine - adverse effects; Azathioprine - metabolism; Chromatography, Liquid - methods; Erythrocytes - metabolism; Female; Guanine Nucleotides - blood; Humans; Immunosuppressive Agents - adverse effects; Immunosuppressive Agents - metabolism; Leukocyte Count; Male; Mercaptopurine - analogs & derivatives; Mercaptopurine - blood; Organ Transplantation; Surgery; Tandem Mass Spectrometry - methods; Thioguanine - blood; Thionucleotides - blood
• ISSN: 0041-1345; 1873-2623
• DOI: 10.1016/j.transproceed.2016.01.084

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 × 108 red blood cells (RBC); median concentration of 6-MMP was 1064.1 (35.78–11,552.9) pmol/8 × 108 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.