Assay of azathioprine, 6-mercaptopurine and a novel thiopurine metabolite in human plasma.
1 A simple, specific assay for 6-mercaptopurine (6-MP) in human plasma with a sensitivity of 10 ng/ml (66 nmol/1) has been developed. 2 6-MP was extracted directly from plasma into toluene using a novel extraction procedure. This involves conversion of 6-MP into a phenyl mercury derivative by its reaction with phenyl mercuric acetate in alkaline plasma and extracting into toluene. Back-extraction of the toluene layer with 0.1N HCl regenerates 6-MP, which is then oxidised to purine-6-sulphonate and assayed fluorimetrically. 3 This assay has been modified to measure azathioprine and a new thiopurine metabolite in plasma. 4 In a kidney transplant patient given azathioprine, 50 mg i.v., conversion to 6-MP was rapid and the plasma half-life of 6-MP was 36 min. 5 These assays are suitable for studying the pharmacokinetics of azathioprine in patients with kidney transplants. The 6-MP assay should also prove useful for studying the pharmacokinetics of the drug in patients with leukaemia.
D001379:Azathioprine / Q000097:blood*; D055598:Chemical Phenomena; D002621:Chemistry; D006801:Humans; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D016030:Kidney Transplantation; D015122:Mercaptopurine / Q000097:blood*; D011687:Purines / Q000097:blood*; D014184:Transplantation, Homologous; D014511:Uremia / Q000097:blood
D011687:Purines; D015122:Mercaptopurine; D001379:Azathioprine