INTRACELLULAR THIOPURINE NUCLEOTIDES AND AZATHIOPRINE MYELOTOXICITY IN ORGAN TRANSPLANT PATIENTS

Aims Despite widespread use of azathioprine in organ transplant recipi ents, the mechanism of its myelotoxicity remains unclear. The aim of t his study was to assess the importance of thiopurine metabolites on bo ne marrow toxicity. Methods We investigated the relationship between i ntracellular concentrations of 6-thioguanine (6-TGN), 6-mercaptopurine (6-MPN) and 6-thioxanthine (6 TXN) nucleotides and the absolute count of white or red cells in forty-seven lung or heart/lung transplant pa tients after oral administration of azathioprine. Results No significa nt correlation between red cell concentrations of 6-TGN or total thiop urine metabolites and white or red cell counts was found, with no diff erence between the sexes. Likewise, high 6-TGN levels were not related to bone marrow depletion. Conclusions These results suggest that red blood cell 6-TGN alone do not predict the haematopoietic toxicity of a zatkioprine.