It's very simple. Once you accept the assumption that people should only be allowed to take narcortics based on a certain level of pain, it's only a matter of time before some stranger is making these kinds of decisions for you.

Would it not be far more reasonable to trust people when they say they need something, and let adults decide for themselves what risks they want to take with their health--and be responsible for the consequences if they turn themselves into junkies?

As long as we continue to think the gov't is our parent, our health will continue to be at the mercy of a government agent--who is no more wise than any other adult.