Can poison, natural or unatural, be the cure for other poisons?

Question: Can poison, natural or unatural, be the cure for other poisons?

Asked by barney to Gioia, Iain, Jo, Leo, Mariam on 16 Jun 2010 in Categories: General.
- Leo Garcia answered on 16 Jun 2010:
  
  A poison is some substance that causes a generally negative effect in living things. But, in limited doses, some poisons can be used to treat illnesses. For instance, chemotherapy drugs are toxic, but we use them to help treat people with cancer.
  
  With regards to your question though, poisonings are usually treated with antidotes, such as antivenom to treat bites from poisonous animals. I suppose that, in turn, overdoses of some these antivenoms could be poisonous – though I’m not sure this means they are classed as poisons in their own right. I think it’s more of a question of word definitions!
- Joanna Watson answered on 16 Jun 2010:
  
  Wow, that’s an interesting question. I have no idea – sorry Barney.
- Mariam Orme answered on 16 Jun 2010:
  
  Poison is a word for any substance that causes harm to an animal or plant. Some poisons have ‘cures’ – other substances that some how stop the poison from doing harm. And in some cases those curative substances can themselves be poisonous.
  
  One example is atropine, which is the very dangerous chemical found in Deadly Nightshade (an extremely toxic plant). It’s used to treat poisoning by some insecticides and nerve gases (maybe you’ve heard of sarin?).
  
  So the simple answer is yes!

Question: Can poison, natural or unatural, be the cure for other poisons?