I'm trying to find a book that was set years in the future about a competition like the olympics, where it was allowed and even ecouraged for competitors to take one specific drug. The only catch was the drug was basically a poison and the government or whoever ran the games were the only people who had the antidote and they only gave the antidote to the winners. It was centered around a woman who initially refused to take the drug and was doing well in the competition, but evetually she had no choice and took the drug. I can't remember the name or who wrote it or how it ended.