| Knight Magenta |
Are the things you want to make mechanically relevent? If you want to just focus on antitoxins and stuff, you can go for Craft(Alchemy) and just make those things you like. If you want to make generic "apothecary-y" things, I think you could flavor the Heal skill as you using your antidotes and stuff.
| Knight Magenta |
Then your best bet is alchemy. That's the catch all skill for making useful non-magic-item magic effects. That being said, nothing stops you from making a Craft(Apothecary) skill and using the rules for craft alchemy to determine DCs and stuff :) Craft skills are a little vague on purpose. You should talk to your GM.