Salinomycin is a polyether ionophore with broad spectrum Gram positive and anti-coccidial activity. Salinomycin has a high affinity for monovalent cations, particularly potassium. Salinomycin is used to control coccidia in animals and for growth promotion in ruminants. Recently, salinomycin has been shown to inhibit cancer stem cells and is >100 times more potent than taxol. While the mechanism of action is unknown, it was noted that among the 60,000 compounds screened, another monovalent ionophore, nigericin, and a chloride channel inhibitor, avermectin, were also active.