The quinoline derivative diiodohydroxyquinoline (INN) or iodoquinol (USAN), can be used in the treatment of amoebiasis. It is poorly absorbed from the gastrointestinal tract and is used as a luminal amebicide. It acts by chelation of ferrous ions essential for metabolism. It was discovered by Adco Co. and introduced as diiodohydroxyquinoline. Susceptibility of Dientamoeba fragilis has been measured. Iodoquinol is an amebocide used against Entamoeba histolytica, and it is active against both cysts and trophozoites that are localized in the lumen of the intestine. It is considered the drug of choice for treating asymptomatic or moderate forms of amebiasis. The mechanism of action is unknown. Iodoquinol is used for diseases caused by moderate intestinal amebiasis.