Please don’t ask the candidates to depict "meth" by body language during the audition. As the kid is exhausted and having a prompt need for meth, more importantly, he knows the nurse has/is able to get meth for him, he would only beg and vent his anger on the nurse like a son does to his father/mother, without rationality. The kid's mind should be pretty straightforward: exhausted, itching, painful, desiring and angry. So, the most important point is whether he can deliver these emotions truly and honestly, say, moaning hoarsely but scream out slightly when one of the sores is torn, pause because of the pain but continue because of the itch, sorrowful to his pain yet full of hatred.