What Is Lactulose?

Lactulose is a type of synthetic sugar that is often prescribed for a serious side effect of liver disease called hepatic encephalopathy, as well as for constipation treatment. The drug is classified as a disaccharide, a carbohydrate culled from the simple sugars galactose and fructose. It works to increase water content of bowel movements, causing laxative-like effects and facilitating looser, more comfortable stools.

When lactulose is ingested, it is broken down in the colon and introduces water from other parts of the body into the organ. This is accomplished through a process of osmosis, which draws the water in and mixes with the waste products being produced. The sugar molecules that comprise lactulose are in part disseminated by the bacteria that reside in the region, resulting in more acids in the gut. The creation of these additional acids prevents water absorption, and the water content is retained in the lower bowel.

The excess water manufactured by lactulose makes stools softer, more frequent, and considerably easier to express. This process is helped along by the increased presence of flatulence, caused by the fermenting of lactulose in the system and readying the body for a bowel movement. The contraction and relaxation of the sphincter muscles, called peristalsis, is another common effect of taking lactulose, further preparing the system for a more comfortable release of waste products.

Lactulose is most often prescribed for chronic constipation. It is commonly given to patients who are experiencing long, recurring periods without a bowel movement. The drug is considered safer than laxatives since it can be taken at elevated doses with no major side effects.

The medication is also prescribed for those with hepatic encephalopathy, a condition that arises from liver disease. Those with hepatic encephalopathy possess high levels of toxic ammonia in the body, and lactulose helps to remove this damaging substance. It is typically one of the first lines of defense in combating hepatic encephalopathy, which, if left untreated, can lead to confusion, coma, and even death.

Lactulose is an oral medication. It is taken once a day for those with chronic constipation, and for those with hepatic encephalopathy, it may be taken up to four times per day. Patients tend to start at a lower dosage, and the amount of lactulose is raised or lowered in conjunction with the particular needs of the patient.

The most common — and desired — side effects of lactulose are loose stools and diarrhea. Other reported side effects include stomach cramps and unusually odorous flatulence. The drug is not prescribed for those with an allergy or sensitivity to galactose, one of the sugars that make up lactulose.