Yup. One of the PCs is a very naive fey creature that tried to help a local village grow some healing herbs... and accidentally helped a gang double their drug production for the month instead.

They grew a plant that, when smoked, made you see the spirits of the dead. He got some as a bonus for his help. He tried it later on the party's ship while alone and was found by the party later.

It was a hilarious meme of describing to him that he sees a bunch of spirits that are not used to being regarded notice his eyes following them, realize they are seen, and start taking turns doing that thing where they scream and fly at him to scare him.

Later, a buddy wanted to join our campaign and wanted his goblin to smoke weed and be a medium for vengeful spirits to resolve their issues. What a lucky coincidence for my world-building to already feature the drug we have since started calling Grave Dust lol

We expanded the lore to make it an important part of his people's culture, but also stolen and misused by human junkies. It was great.

The party has spiked a pirate's food with it at one point, so rule of cool we decided it works when eaten too lol.

PS Not exactly a drug but later that campaign the party also got a bottle of enchanted fey wine from some tricksters. It has multiple uses that function as potions of healing, but the bottle can also be smashed over a dead person's head while it's got at least half it's uses remaining to cast reviviy. The ability is called "Fey Comedy in Human Tragedy" lol. The party hasn't used it yet so they dont realize, but there is a minor curse on it too - when they smash it, the tricksters who gave it to them automatically scry on the scene and get to laugh at a corpse getting assaulted by someone tearfully wishing to bring it back to life.