my husband is taking ultracet for painful knees and hips. Ultrac...

my husband is taking ultracet for painful knees and hips. Ultracet has taken away the pain and my husband functions normally now. I worry that he is becoming addicted.(if that is possible) as he has ran out of the medication and has had a terrible time with very restless legs and he can't go to sleep. He paces the floor all night. He also scratches and seems to have excessive thirst while on the meds. He takes four or five at a time a couple times a day.