I have a character who is a middle aged black woman who, for the past four years, has been in a mental hospital being treated for schizophrenia. In the story she refuses to eat and is fed via an IV drip. I am looking for a poison that could be injected into her IV drip in order to kill her. It needs to have a sudden and violent reaction when it reaches her bloodstream since her youngest son leaves the room for fifteen minutes or so and when he returns doctors are already rushing to her room to save her. This isn't even a major plot point but it is a detail that I'd like to get straight before I continue with the story.