Specifically:
Original song: Bad Apple!! (track 7 here) from the game 東方幻想郷 ~ Lotus Land Story (Touhou Gensoukyou ~ Lotus Land Story), composed by 上海アリス幻樂団 (Team Shanghai Alice), the maker of Touhou Project, whose only member is ZUN.
Remix: Bad Apple!! from the album Lovelight by Alstroemeria Records, arranged by Masayoshi Minoshima, lyrics by Haruka, vocals by nomico
Original shadow art video: Posted by user Anira on NicoNicoDouga, reposted on YouTube by Masayoshi Minoshima.
A. Youkai in Touhou aren't affected by human medicines or poisons in the same way humans are. They won't be healed by human medicines.
B. Youkai in Touhou are very much capable of getting drunk, because getting drunk has a storied tradition of connecting one to the spirit world and many spiritual associations. They do it a lot.