I DO use metamucil for my Quincy...Those who have heard the story before, Quince was paralysed in the lower limbs and as he got over that, a small amount of neuro deficit was left and was the cause of a great deal of contsipation where enemas, lactulose, probiotics and other remedies just did not work long term. He had to be manually evacuated 3 times and that many anesthetics just isn't good either! My vet was starting to consider radical colon surgery so I was motivated to make something work!
He is doing great now but I do have to maintain him on prepulsid twice a day, lactulose, twice a day and I give him a quarter tesapon of metamucil every morning in his breakfast meal. I DO HOWEVER, MIX AT LEAST 25CC OF WATER INTO HIS FOOD WHEN HE GETS IT. I have spoiled this guy rotten, and he eats the food from a spoon I feed it to him with. That way I know, he gets the full dosage, and no one else is getting the metamucil. I also wait about an hour before giving him his other meds in the morning as metamucil can coat the meds and prevent absorption when given at the same time. I also mix his lactulose with an additional 10cc of water each time, so increasing his fluid intake also helps the chronic constipation with him.
I had heard about mineral oil, but was always afraid of kitty moving or jerking and ending up aspirating the stuff. It scared me so I avoided it.