Here is my theory - I think that all opiates can cause pseudo-hallucinations, because they tend to push the user strongly to the hypnogogic state, the state in between being fully awake and being totally asleep - you know, when you're laying there nodding off, your thoughts are blurring, eyelids getting heavy, almost half asleep, visual and oral hallucinations are common in this state, but they should instantly go away if you do anything to wake yourself back up, like sitting up or something. I have had quite a few aural and visual hallucinations while nodding off on oxy - right before I fall asleep, I hear sounds, see things on the walls, but if I move around at all they go away. People who are sedated with morphine during surgery also report hallucinations in half consciousness pretty often too. Maybe other sleep aids such as dramamine and ambien induce hallucinations in this manner too, by keeping you in the hypnogogic state where hallucinations naturally occour? Just a thought.