Which medications in the drug class Laxatives, Osmotic are used in the treatment of Constipation?

Updated: Jul 05, 2019
  • Author: Marc D Basson, MD, PhD, MBA, FACS; Chief Editor: BS Anand, MD  more...
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Laxatives, Osmotic

Osmotic agents are useful for long-term treatment of constipated patients with slow colonic transit that is refractory to dietary fiber supplementation.

Lactulose (Constulose, Enulose, Generlac, Kristalose)

Lactulose produces an osmotic effect in the colon, resulting in bowel distention and stimulation of peristalsis.


Sorbitol is a hyperosmotic laxative that has a cathartic action in the GI tract.

Polyethylene glycol solution (Miralax)

Polyethylene glycol is typically used in large volumes for bowel preparation and washout before surgical or endoscopic procedures. It is now being used in smaller volumes as an osmotic (but not hyperosmotic) agent.

In theory, there is a lower risk of dehydration or electrolyte imbalance with isotonic polyethylene glycol than with hypertonic sugar solutions. The laxative effect is generated because polyethylene glycol is not absorbed and continues to hold water by osmotic action throughout the small bowel and the colon, resulting in mechanical cleansing.

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