In the USA, dantron is not used because it is considered to be a carcinogen.
In the UK it is considered a possible carcinogen and so its licence is restricted to patients who already have a diagnosis of terminal cancer. It is mainly used in palliative care to counteract the constipating effects of opioids. Its British Approved Name was danthron, but it has now been changed to "dantron", the recommended International Nonproprietary Name.
Dantron has the notable side-effect of causing red-colored urine.