It is intoxicating to believe you know truth. That what I've read or been taught is always the only way of seeing something. It seems a literal take on the precepts, particularly the fifth precept (do not take or distribute intoxicants) is one that many feel should be "taken" at face value. To be sure, I hardly ever drink (I have a three quarter full bottle of Jagermeister that has lived in my freezer for over ten years now) and I do not take drugs explicitly for intoxication. But, I reserve the right to take intoxicating medications (ie morphine, oxycodone etc) if I were to have surgery or an accident. Likewise, I do not feel distributing intoxicating pain meds to my patients violates the precepts as to not do so would cause harm.
We awaken to Buddha nature, we do not learn it from the words or actions of others. Just because a teacher defines something one specific way, I am not necessarily bound to that understanding. A true teacher is but a finger pointing to the moon. It is the moon and not the finger we should be paying attention to. If we follow our ancestors blindly not only are we attached to their finger (teachings), we are also guilty of dragging their corpses though the streets.
I am reminded of a dharma story I heard though I forget from whom where a dharma center had a pet cat who would always go into the meditation hall while it was in use. One day, the abbot tied the cat to a leash which was attached to a pole outside the meditation hall. Years of this went by. The abbot passed away and many practitioners came and went. All the while, the cat was tied to the post outside (it was a very long-lived cat!). One day the cat died. The practitioners were so distressed! They couldn't meditate! They demanded the abbot find a new cat right away. After all, how can one meditate without first tying a cat to a pole!
All of the precepts are real and important (and maybe real important). To always be conscious of the precepts and apply them to life, moment by moment, is much more real important-er. Don't ever say "The ancestors said thusly and therefore I will always act accordingly." You are the ancestors, you are the teachers, you are Buddha and you are impermanent. Be awake to it.
If you say "Zen precepts are held in my right hand, there is nothing else," you have already lost zen so why then should you keep holding the precepts?
Look again, your palm is empty.
If you say "Administering drugs for medical reasons is acceptable," I ask "Is it so stated in the precepts you accepted?"
If you still answer "Yes," I ask "Did you need to have the words on paper to know what was the right thing for you to do?"
Be awake.
Moment by moment we create, destroy and recreate the precepts. In accepting the precepts, we accept that their current form is impermanent. Otherwise, we can become attached to their form. We risk becoming a potential agent of suffering to ourselves or others.