Converted to thioinosinic acid by the enzyme hypoxanthine-guanine phosphoribosyltransferase. Thioinosinic acid then inhibits reactions involving inosinic acid. Cross-resistance with thioguanine has been observed. Lymphoblastic leukemia, especially in children. Acute myelogenous and myelomonocytic leukemia.
Effectiveness varies depending on use.
The drug is not effective for leukemia of the CNS, solid tumors, lymphomas, or chronic lymphatic leukemia. Use during lactation only if benefits clearly outweigh risks. There is an increased risk of pancreatitis when used for inflammatory bowel disease. Hepatotoxicity, oral lesions, drug fever, hyperuricemia. Produces less GI toxicity than folic acid antagonists, and side effects are less frequent in children than in adults.