It is used to treat some kinds of cancer.
Thioguanine interferes with the growth of cancer cells, which are eventually destroyed.
Since the growth of normal body cells may also be affected by thioguanine, other effects will also occur. Some of these may be serious and must be reported to your doctor. Other effects may not be serious but may cause concern. Some effects may not occur for months or years after the medicine is used. Before you begin treatment with thioguanine, you and your doctor should talk about the good this medicine will do as well as the risks of using it.