The winter update said that you should be able to poison weapons now. However, it seems completely bugged.
Basic poison only gives me an option to drink it, and the description says that it heals for 2d4+2 healing!
There's also something messed up with the tags on the item: TOOLTIP/&TAGPOSIONTITLE seems broken and then it does have the HEALING tag, which just seems wrong.
I haven't found any recipes for anything other than Basic Poison, nor have I found any poisons beyond the Basic Poison. So maybe it's just this one item that is broken and I just haven't found a working one.
Version 0.4.14 b - Public