Which laxative takes the longest to act?

Psyllium (Metamucil) is a bulk-forming laxative that works by absorbing water in the intestines, which increases the bulk of the stool and helps to stimulate bowel movements. This process typically takes longer to produce a result compared to stimulant laxatives or osmotic agents because it requires sufficient hydration and time for the fibers to swell and impact the gut.

In contrast, stimulant laxatives like bisacodyl and senna act more quickly by stimulating the intestinal muscles, leading to faster bowel movement. Magnesium hydroxide, an osmotic laxative, also tends to produce effects more swiftly by drawing water into the intestines, thereby promoting bowel evacuation.

Given the nature of how psyllium works, it is understood that it requires time for the body to process and respond to increased dietary fiber, making it the slowest acting of the mentioned laxatives.