azathioprine UK /ˌeɪ.zəˈθʌɪ.ə(ʊ).pɹiːn/US /ˌæz.əˈθaɪ.əˌpɹin/ noun1 •A purine antimetabolite immunosuppressant used in organ transplant and autoimmune diseases to prevent rejection.The patient was treated with methylprednisolone, cyclophosphamide, and azathioprine, as well as burn center protocol care with daily tankings. — 1993 formsazathioprines