In a long-time campaign of mine, one of the cultures was a mix of the Nyissans from David Edding's books and the Aztecs. They had drugs for absolutely everything: combat, medicine, religious ceremonies, commerce, sports, whatever.
I remember a PC walking into a shop where the air was heavily laden with incense and other things. He had only a hazy memory of what happened there, but an hour later he found himself wandering the bazaar with a stuffed miniature mammoth under one arm, minus quite a lot of gold, and wondering what happened. I believe the mechanic was simply save vs poison with some modifier, if the save failed they spend 1d6x10 on something random in the shop.
