 Antimony @-@ based drugs , such as <unk> <unk> , are also considered the drugs of choice for treatment of <unk> in domestic animals . Unfortunately , as well as having low therapeutic <unk> , the drugs are poor at penetrating the bone marrow , where some of the <unk> amastigotes reside , and so cure of the disease – especially the visceral form – is very difficult . Elemental antimony as an antimony pill was once used as a medicine . It could be reused by others after ingestion and elimination . 
