Scientific Essay from the year 2017 in the subject Medicine - Pharmacology, grade: 1, Egerton University, language: English, abstract: Azathioprine drug has been in clinical use since its discovery in 1957 in which it was used as a chemotherapy drug. It produces a biological metabolite known as 6-mercaptopurine which is a metabolically active form and it acts as an immunosuppressant. In regard to pharmacokinetics of azathioprine, this drug functions by inhibiting purine synthesis in the body leading to the impairment of cellular proliferation because there is lack of adequate DNA molecules for the formation of new cell. In particular, immune cells are prevented from multiplication owing to the inhibition of purine synthesis in the lymphoid tissues. It has been found out that the inhibition of DNA synthesis hinders nucleotide salvage process which ensures continuous production of lymphocytes for immune responses, especially during infections (Desler, Lykke& Rasmussen, 2010). Therefore, this research paper focuses on azathioprine genetic polymorphisms.