Zelnorm has been thoroughly studied in clinical trials, with many people having been evaluated. In these studies, side effects occurring in the group of people taking the drug are always documented and compared to the side effects that occur in a similar group of people not taking the medicine. Based on these studies, the most common Zelnorm side effects include:
Headache -- up to 15 percent of people
Abdominal pain (or stomach pain) -- up to 12 percent of people