Gabby Grace,
I am assuming he is not taking the medication for chronic pain? From your post, I gather that your grandson is just flat out telling the doctor lies? How much is this doctor giving and what medication?
I would say what can be done depends on how much meds this doc is handing out and what the meds are. If your grandson is going in once a month and getting 30 Lortab for "muscle pain" and that is it, there is probably not much that can be done-as this is a reasonable dose and they would have to prove your grandson is fibbing. However, if your grandson is getting 120 Oxycontin a month for "muscle pain" that is a different story. I would think you could call the state medical board or something....maybe obtain some records from the pharmacy and send a written letter along with the pharmacy info. (Is your grandson on your daughters insurance? If so, ask the insurance to send you their Rx records.) Things could get sticky with the HIPPA laws, but where there is a will there is a way!!

Good luck.