It's probably done solely for differentiating the product. Ephedrine and norephedrine are essentially analogues of epinephrine and norepinephrine (aka adrenaline and noradrenaline). I haven't found any significant differences between E and NE. Both are catecholamines, both are released from the adrenal medulla, and both are classified as biogenic amines.
About the only difference between the two that I know of is the number and area of brain neurons upon which each hormone exhibits action.