Dietary fiber and related bulk-forming laxatives

Dietary fiber and related bulk-forming laxatives

A high-fiber diet is the most natural way to prevent or treat constipation. Dietary fiber is the part of plants not digested in the small intestine.

Bulking up

Bulk-forming laxatives, which resemble dietary fiber, contain natural and semisynthetic polysaccharides and cellulose. These laxatives include:

• methylcellulose
• polycarbophil
• psyllium hydrophilic mucilloid.

Pharmacokinetics

Dietary fiber and bulk-forming laxatives aren’t absorbed systemically. The polysaccharides in these drugs are converted by intestinal bacterial flora into osmotically active metabolites that draw water into the intestine.

Excretion

Dietary fiber and bulk-forming laxatives are excreted in stool.

 

Pharmacodynamics

Dietary fiber and bulk-forming laxatives increase stool mass and water content, promoting peristalsis.

 

Pharmacotherapeutics

Bulk-forming laxatives are used to:

• treat simple cases of constipation, especially constipation resulting from a low-fiber or low-fluid diet
• aid patients recovering from acute myocardial infarction (MI) or cerebral aneurysms who need to avoid Valsalva’s maneuver (forced expiration against a closed airway) and maintain soft stool
• manage patients with IBS and diverticulosis.

Drug interactions

Decreased absorption of digoxin, warfarin, and salicylates occurs if these drugs are taken within 2 hours of taking fiber or bulk-forming laxatives. 

 

Warning!

Adverse reactions to dietary fiber and related bulk-forming laxatives

Adverse reactions to dietary fiber and related bulk-forming laxatives include:

• gas
• abdominal fullness
• intestinal obstruction
• fecal impaction (hard stool that can’t be removed from the rectum)
• esophageal obstruction (if sufficient liquid hasn’t been administered with the drug)
• severe diarrhea.