Metalloids can severely harm human physiology in a toxicological sense if taken up from the environment in acute high doses or chronically. However, arsenic or antimony containing drugs are still being used as treatment and are often the sole regime for certain forms of cancer, mainly types of leukemia and diseases caused by parasites, such as sleeping sickness or leishmaniasis. In this chapter, we give an outline of the positive effects of arsenicals and antimonials against such diseases, we summarize data on uptake pathways through human and parasite aquaglyceroporins and we discuss the progress and options in the development of therapeutic aquaporin and aquaglyceroporin inhibitor compounds.