When ordinary over-the-counter laxatives fail to work, doctors usually turn to one of two osmotic laxatives to treat people with constipation. Osmotic laxatives are nonabsorbable and nonmetabolized. Their mechanism of action is to increase the amount of water in the colon.
Lactulose and Polyethylene Glycol (Macrogol) have been shown to be effective and safe treatments for chronic constipation. The former is a semisynthetic disaccharide resulting in osmotic diarrhea with low fecal pH while the latter is an inert polymer that sequesters fluid in the bowel.
However, there is no definitive data as to which provides the best treatment.
Now, according to the results of a systematic review reported online July 7 in the Cochrane Database of Systematic Reviews, polyethylene glycol "works a bit better" than lactulose at helping patients who are desperate to get things moving.
The researchers found that polyethylene glycol was better than lactulose in several areas, including the number of stools per week and the form of the stool. Those who took polyethylene glycol also had less need for other medications to treat their constipation.
Children who took polyethylene glycol had less abdominal pain, but there was not a difference in adults between the two drugs.
The two drugs are "supposed to have no side effects," Dr. Richard L. Nelson, the review co-author said, and indeed, they do not harm the colon over the long term like some other laxatives. However, the review points out that both drugs can cause diarrhea, while polyethylene glycol can cause nausea and pain while lactulose can lead to bloating and flatulence.
Reference:
Lee-Robichaud H, Thomas K, Morgan J, Nelson RL. Lactulose versus Polyethylene Glycol for Chronic Constipation. Cochrane Database Syst Rev. 2010 Jul 7;7:CD007570.
Lactulose is available as Duphalac. Polyethylene glycol is found in Forlax.
We will talk about prevention of constipation tomorrow.
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