This study is for kids aged 12 to 17 with IBS-C, a tummy problem where you get constipated often. The study checks how safe and effective tenapanor, a medicine, is for treating IBS-C. Participants will be divided into groups to receive either tenapanor or a placebo (a pill with no medicine) for 12 weeks. They must use an eDiary, a special device to record their symptoms every day. The study starts with a 2-week screening to see if kids are eligible. During the 12 weeks, they will visit the study center every two to four weeks for safety checks.

• The study lasts for about 3 months, with several visits to the clinic.
• Participants will use an electronic diary to track their symptoms daily.
• Eligible participants must be willing to stop using other laxatives during the study.

If you have certain health conditions, like celiac disease or recent surgeries, you might not be able to join. It's important to talk with your parents and doctor to see if this study is right for you. Participants will not be given compensation for participating in this study.