lubiprostone [ Amitiza,Prostan-1-oic acid, 16,16-difluoro-11-hydroxy-9,15-dioxo-, (11alpha)-,RU 0211,RU-0211,RU0211,SPI 0211,SPI-0211,SPI0211 ] a bicyclic fatty acid prostaglandin E1 derivative known as prostones; a chloride channel opener used to treat constipation