What Is an Osmotic Laxative?

An osmotic laxative works to encourage a bowel movement by bringing more water into a person’s intestine, which has a softening effect on the stools. As a result, a person may have an easier time passing them. There are both prescription and over-the-counter (OTC) osmotic laxatives.

Polyethylene glycol (PEG) is an example of an OTC osmotic laxative. Widely known by the brand name Miralax®, this medication is sold as a powder that a person can mix with the beverage of his choice. Though the results are not immediate, this medication helps the intestine absorb water, resulting in softer bowel movements. Usually, the use of this medication results in a bowel movement within a couple of days. While it can cause side effects, some people report that they are mild in comparison to those experienced with other OTC laxatives.

Sometimes doctors prescribe prescription laxatives like lactulose for chronic cases of constipation. Also known by the brand names Cholac®, Generlac®, and Kristalose®, this medication is a type of man-made sugar that the body doesn’t digest. It is usually taken once a day in liquid form and travels to the intestine, pulling water into the intestine and producing a bowel movement within two days. Lactulose can cause minor side effects like other laxatives, but some patients develop severe vomiting or stomach pain while taking this osmotic laxative. In such a case, a doctor’s attention is usually warranted.

While this type of laxative often proves effective, it can also cause a range of side effects. Among the most common a person might suffer are bloating and cramping in the abdominal region and the passing of gas. Some people also experience diarrhea and become nauseated while taking these laxatives. Such symptoms are usually only temporary and fade after the medication has worn off. When a person uses laxatives too often or takes too much of one, however, dehydration can develop as well.

There are many brands of laxatives that work osmotically, and they are generally considered safe. Patients are typically advised to avoid taking an OTC osmotic laxative on a regular basis, however, as frequent use can cause the body to become dependent on it. With chronic constipation, a patient may need long-term treatment with a laxative but might consume more fiber, drink more water, and increase his physical exercise in an effort to help his body naturally.