This study is about testing a medicine called Tenapanor for people with Chronic Idiopathic Constipation (CIC). CIC means you often have trouble with bowel movements, and doctors don’t know why. During the study, participants will take either Tenapanor or a placebo (a harmless pill) for 26 weeks. A placebo is used to see if the medicine really works. There are three doses of Tenapanor being tested: 5 mg, 25 mg, and 50 mg, taken twice a day. After 26 weeks, there is an additional 4-week period where no medicine is taken, to check safety.

Before joining, there's a 2-week screening period to make sure you’re eligible, including health checks and using an electronic diary (eDiary) to record constipation symptoms. If eligible, you visit the clinic every 2 to 6 weeks for checks. The study is double-blind, meaning neither you nor the doctors know if you’re taking the real medicine or placebo.

• Study Duration: 26 weeks of treatment + 4 weeks of follow-up
• Clinic Visits: Every 2 to 6 weeks
• Participant Requirements: Eligible adults aged 18-80 with CIC