Magnesium hydroxide is effective for the relief of occasional constipation.* It is an "osmotic laxative" and uses water to flush fecal matter out of the intestines. When water is drawn into the intestines, fecal matter absorbs the excess water as it forms into bowel movements. As this material swells, it puts pressure on the sides of the intestines, initiating peristalsis – the act of moving the bowels. It is as effective as stimulant laxatives such as cascara and senna.