**Patiromer for Treatment of Hyperkalaemia in Children Under 12 Years of Age** **Study Purpose:** This study is testing a medicine called patiromer to see how it works (pharmacodynamic effects), how safe it is, and if kids can handle it well. It’s for children under 12 who have hyperkalaemia, which means they have too much potassium in their blood. **What’s Involved:** - *Length of Study:* 28 days of treatment. - *Visits Needed:* The child will need to visit the study site regularly. - *Safety Checks:* Children will be checked for any side effects or reactions. **Who Can Join:** Kids under 12 with high potassium levels can join if they can take medicine regularly. They must not turn 12 during the 28-day study. Girls who might have babies must not be pregnant and must use birth control. **Who Can’t Join:** Babies born too early, children with certain kidney problems or serious stomach issues, or kids scheduled for a kidney transplant soon can’t join. Also, kids with allergies to patiromer or certain medications are not allowed. The study requires a parent or guardian to help with visits and medication.