Just something I was thinking about. Does your setting have drugs mentioned often, or even at all? If they are listed, are any illegal? If they are legal, do the player characters use them? Are there any benefits or penalties?
Drugs I would allow as legal in any setting I run:
Wine, beer, ale, tobacco, marijuana.
Drugs that would be legal in most places:
Pretty much the only drugs I think would be made illegal are ones that cause the user to become violent (like bath salts or meth can do).
Of course, in a fantasy setting, there would be magical potions and other substances that would be available to the rich. Likely, these would all be legal, but really expensive.
Drugs that grant magical powers (such as black lotus in my games), are almost always illegal for anyone not connected to a temple. The priests reserve these for themselves.
In some societies, even low level potions might be heavily regulated. Imagine if Charm Person potions (or scrolls) are illegal, due to how much they would be abused.