Hydrophillic colloids, such as Metamucil, are indigestible fiber. The fiber will take 1-3 days for it to work. Once it gets to the intestinal tract it increases bulk and attracts water to it which then increases motility. In order for this to work, they must also consume water. Since it takes time for it to work, these colloids will not acutely treat constipation. This is primarily meant for individuals with chronic constipation so they take this day in and day out.
Laxatives in general can also be addicting/habit-forming but the hydrophillic colloids are not habit forming because it’s fiber and fiber should be in your diet anyway. It’s simply replacing something that’s not in your diet.
When we review diarrhea, we will bring up this drug once again. How could the same drug be used for constipation and diarrhea on the opposite sides of the spectrum? Because the fiber will draw the excess water towards it and absorb it. With diarrhea though, you wouldn’t want to drink water with it though!
- Indigestible fibers
- Increases bulk which increases water in intestinal lumen
- Leads to increased motility
- Must consume with water
- Onset of action: 24 to 72 hours (not for acute use)
- Example: Psyllium Seed (Metamucil®)
- Use: Chronic constipation
