Zelnorm works by stimulating certain serotonin receptors in the digestive tract. This helps the muscles of the digestive tract to move food through more quickly, which helps to treat and prevent constipation. It also helps to make the nerves in the digestive tract less sensitive, leading to decreased feelings of pain and bloating.
There have been several studies looking at how well Zelnorm treats IBS with constipation and chronic idiopathic constipation.
Irritable Bowel Syndrome (IBS) With Constipation
Several studies have looked at using Zelnorm for IBS with constipation in women. In these studies, women were asked to rate their symptoms of IBS as: completely relieved, considerably relieved, somewhat relieved, unchanged, or worse. In these studies, 31 to 35 percent of women who took Zelnorm felt completely or considerably relieved after the first month, compared to 17 to 22 percent of women who did not take it. More women (both those who took it and those who did not) felt completely or considerably relieved after three months of treatment.
Two studies have looked at Zelnorm as a possible IBS medication in men. These studies did not show any difference between the men who took Zelnorm and the men who did not. This could mean that it is not effective for IBS in men, or it could mean that the studies did not look at enough men to be able to notice a difference.
Chronic Idiopathic Constipation
Two studies have looked at using Zelnorm for long-term constipation with no apparent cause in people less than 65 years old. In these studies, 43 to 45 percent of people who took it had at least one normal bowel movement per week, compared to only 25 to 28 percent of people who did not take Zelnorm. People who took it also had less straining, bloating, and pain.
When the drug was looked at for chronic idiopathic constipation in people age 65 and older, these studies did not show any difference between people who took Zelnorm and people who did not. This could mean that it is not effective for constipation relief in people 65 and older, or it could mean that the studies did not look at enough people ages 65 and older to be able to notice a difference. Zelnorm has not been studied as a treatment for constipation in children or for infant constipation.
(Click Causes of Constipation to learn about what can cause constipation.)