Well we know it is an extraordinary class ability (Ex)
Page 221 and 554 will give you a few words on what that means, but basically through training you have learned to do something that is non magical and superhuman.
If you use the argument that your druid shape shifting powers allow your body to instantly change itself to adapt to the poison.
lights flickered so going to send as is incase power cuts
If that doesn't work use the spell Polypurpose Panacea(Ultimate Magic) to get what you need.
One of it's effects: "Intoxication: You feel comfortably intoxicated for 1 hour, as if you had a few alcoholic beverages."
It's a level 1 wiz/sorc or alchemist so you will need to buy a potion for 50 gold. Not terribly expensive for a level 9+ character.