(This little personal recollection should probably be shared under a heading like "Dumb college kids caught doing something dumb in Mexico on spring break". But so be it.)
They were called Cyclopal, little white pills sold openly in Escuela De Readaptacion (School of Redaptation, or prison) in Hermosillo, Sonora back in 1970. They were a path to sweet dreams, but, being codeine based, something that I had no attraction for. (I stuck with the pot which was plentiful, strong, and cheap inside.)
Crazy Raul, though, I figured that he may have had an addiction going. Since there were folks in there whose only offense was being homeless and he was so dirt poor, I always figured that he just didn't fit in on the outside. But on the visiting days he was a hustling machine.
The visitors came directly into the prison interior and it created a real holiday atmosphere twice a week. Food, booze, and crafts for sale, children running the halls, roaming Mariachi bands, couples arranging places to be discreet. That sort of thing.
Raul hawked whatever someone was willing to give him a commission on (ship in a bottle, woven baskets, and braided horse hair hatbands were always big sellers), and he bought pills as fast as he cleared enough for one. Before the end of the visit he was falling down high, but, I think, loving it. And then he needed to keep it going so he hocked what few meager things he had. When we saw him down to his underwear that was the signal that this cycle was over, and that he would have to be basically naked and straight for the next couple of days.
And then it would start over. His clothes were given back to him first thing on visiting day on trust that what he owed on them would be paid from his first sales, and he never failed, because he would have been out of business, and out of drugs, if he did.