HorrorSpeak---Terror Awaits You in Every Forum!!!!: Need help finding title of late 80's/early 90's horror movie

Hi all,

I watched a horror movie with my parents when I was really young. I don't remember the title, nor much of the plot, but there is one scene that I remember very well. I would like to view this movie again, and hopefully one of you can tell me the title based on the one scene that I do remember. Here goes:

There are a bunch of drug addicts getting high in a nondescript house/apartment/etc. One of them gets sicks. His friends put him in a bedroom. A little while later a woman goes to check on him. When she goes into the room and closes the door he turns into some sort of monster or demon. The woman starts screaming. A man outside of the room hears the screaming and goes into the room to see what the fuss is about, at which point the monster/demon thing turns back to normal before the door opens. The man checking on the screaming doesn't see anything amiss, although the girl is telling him about what she saw. The man doing the checking tells her that she is crazy, closes the door and leaves, at which point the sick man turns into a monster again.

I know this isn't a lot to go on, but if you have ever seen this movie and could tell me the title, I would appreciate it.