Salinomycin sodium is prepared from salinomycin taking advantage of the acidic carboxylic acid which ionises and readily forms the salt in sodium hydroxide solutions. The sodium salt is the preferred formulation in animals to prevent coccidiosis and to promote growth. Salinomycin has a high affinity for monovalent cations, particularly potassium. Recently, salinomycin has been shown to inhibit cancer stem cells.