they had it in Fallout and in a mission for shivering isles so it wont be too hard for addiction
there definetely wont be a snorting action for moonsugar.. bethesda would be fined huge amounts and it would damage their company image.. its for similar reasons why they renamed all the drugs in the fallout series after austrailia had issues with it
They only renamed "morphine" to "Med-X", all of the other fictional drugs had been in previous Fallout games.
On topic, I think it's time they implemented an addiction system for Skooma and Moon Sugar. It's never made sense that NPCs can get addicted to it, but not the player character. Maybe you could base the addiction chance off of Endurance (to combat the physical dependency) or Willpower (to combat the mental dependency)?