Imuran is a medication used to suppress the immune system and prevent rejection in organ transplant patients. Synonyms for Imuran include azathioprine, Azasan, Azamun, Azapress, Azathioprinum, and Imurek. Azathioprine is the generic name for Imuran. Azasan and Azamun are both brand names for the generic medication. Azapress is another brand name used for Imuran. Azathioprinum is another alternative name for the medication used in some countries. Imurek is the brand name for azathioprine in Germany. All of these names refer to the same medication.