Specific Agents and Mechanism of Action

The many available types of laxatives are usually classified by their apparent mode of action.22 27 35 Often, two different laxatives, either from the same class or from two different classes, are combined in the same commercial preparation. Some of the more common laxatives, listed by their apparent mechanisms of action, are in Table 27-4. The major laxative classes and rationales for their use are outlined in the next few sections. 

Bulk-Forming Laxatives. These agents absorb water and swell within the lower GI tract. The increased size of the water-laden laxative stretches the bowel, thus stimulating intestinal movement (peristalsis). Bulk laxatives commonly contain natural and semisynthetic dietary fiber such as bran, psyllium, and methylcellulose. 

Stimulant Laxatives. The precise mechanism of stimulant laxatives is not known. They may activate peristalsis by a direct irritant effect on the intestinal mucosa or by stimulating the nerve plexus within the 

Bulk-forming Methylcellulose Psyllium Citrucel Fiberall, Metamucil 

Casanthranol Doxidan Liquid Gels Peri-Colace 

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