I have used slippery elm for a long time, with a cat who was prone to constipation/obstipation. I make a syrup with 1 cup water and 1 tablespoon slippery elm powder, boiling it until it thickens. When it cools I can pour a tablespoon or two over his wet food and he laps it up. He also takes 1/4 teaspoon Miralax daily. He's coming up on 20 years, so obviously neither of these has hurt him.