a compound comprising a prodrug of a prostaglandin ep 4 agonist , wherein said prodrug is an ester , ether , or amide of an amino acid is disclosed herein . maintenance of the colonic mucosal barrier by method comprising administering a therapeutically effective amount of a prostaglandin ep 4 agonist to a colon of a mammal is also disclosed herein . dosage forms , medicaments , and compositions , related thereto are also disclosed .