Ramipril vs. Amlodipine in Pediatric Hemodialysis Patients

The goal of this clinical trial is to learn if Ramipril works better than Amlodipine to reduce endothelial dysfunction in pediatric patients (aged 5-18 years) with end-stage kidney disease undergoing maintenance hemodialysis and diagnosed with hypertension. It will also learn about the safety, efficacy, and impact on quality of life of both drugs. The main questions it aims to answer are: * Does Ramipril lower asymmetric dimethylarginine (ADMA) levels-a marker of endothelial dysfunction-more effectively than Amlodipine? * Does Ramipril preserve Fetuin-A levels-a marker of vascular calcification-better than Amlodipine? * How effectively do Ramipril and Amlodipine control blood pressure and improve disease-specific quality of life? * What side effects or medical problems do participants experience while taking Ramipril versus Amlodipine? Researchers will compare Ramipril to Amlodipine to see if Ramipril exerts superior protective effects on vascular health and endothelial function beyond blood pressure reduction. Participants will: * Stop taking previous antihypertensive medications (ACE inhibitors or calcium channel blockers) for a 2-week washout period prior to baseline testing * Take either Ramipril or Amlodipine daily for 3 months * Continue standard hemodialysis sessions (3 times per week, 3-4 hours per session) * Provide pre-dialysis blood samples at baseline and after 3 months of treatment * Complete the Pediatric Quality of Life Inventory (PedsQL™ 3.0 ESRD) questionnaire at baseline and after 3-month * Undergo regular blood pressure checks, clinical monitoring, and weekly phone check-ins to monitor safety and potential side effects