As expected the majority of clinical data, guidelines and opinions on the use of urea and ure-Na for hyponatremia are in the adult population. That data can be found in the Physicians page of this site.
Ingredients in descending order: synthetically derived urea powder, natural flavors, maltodextrin, citric acid, calcium silicate, sucralose.
For some, especially people with diabetes the caloric content of ure-Na is important. Each sachet of ure-Na contains less than 15 calories. The calories are derived from the maltodextrin.