Cetalkonium chloride is a cationic quaternary ammonium surfactant, which is used for the treatment of mouth ulcers and sores (Bonjela trade name). It is also serves as an excipient for the purpose of long-term stabilization of ciclosporin ocular formulation, used in patients with dry eye syndrom (Ikervis trade name). The antibacterial properties of cetalkonium can be explained by its detergent character. Once applied, cetalkonium blocks the survival of biofilm forming bacterias.