Is it dangerous to wake someone who's experiencing a night terror?

It can be: If someone is experiencing a true night terror (not nightmare) s/he's in stage 3-4 sleep (not rem). Even though eyes may be open, s/he is not "awake" and you may not be able to awaken him/her if you try. Sometimes the person may thrash out violently -- which could be dangerous. If these episodes are happening often, her doctor may suggest a medicine that interferes w/stage 4 sleep, for a time.