Azathioprine metabolism in kidney transplant recipients.

Abstract

Azathioprine metabolite concentrations were studied in 54 kidney transplant recipients. Thirty‐seven of these patients were studied over a 6 month period to investigate the intrapatient variation in metabolite concentrations. All patients had stable functioning grafts and normal peripheral white blood cell counts. The metabolites measured were plasma 6‐mercaptopurine and red blood cell 6‐thioguanine nucleotide. There was no correlation between azathioprine dose and plasma 6‐mercaptopurine concentration but there was a significant correlation between dose and red blood cell 6‐thioguanine nucleotide concentration (rs = 0.41, P less than 0.005). The individual transplant recipient showed little variation in metabolite concentrations over several months. Using this group as a control we studied metabolite concentrations in patients with kidney transplants who developed leucopenia. Our preliminary findings indicate that elevated red cell 6‐ thioguanine nucleotide concentrations, above the control range, can be associated with bone marrow depression. 1984 The British Pharmacological Society