These make the intestines hydrate (concentrate more water within), thus softening the stool. There are two types:
1. Saline laxatives
These work on the small and large intestine and take from 30 minutes to 6 hours to work. They attract and retain water in the hollow of the intestine, the tube of the intestine (intestinal lumen), thus softening the stool. They also increase intraluminal pressure.
Examples: Dibasic sodium phosphate, milk of magnesia (magnesium hydroxide), Epsom salt (magnesium sulfate), monobasic sodium phosphate, sodium biphosphate, magnesium citrate.