Addictive hallucinogens are a major plot point in The Lost City
Dungeon Module B4 (Tom Moldvay - 1982; written for Moldvay Basic), while not containing rules for drug use by PCs, has an extensive backstory plot involving drugs.
Long before the characters stumble upon the ruins of a city in the desert, it was once the thriving capital of a fertile kingdom. Digging for a grand pyramid awakened an ancient monster, which eventually came to be worshipped by the citizens. A cult sprang up around the monster, and the cultists
began to look for strange pleasures. They sought oblivion in rare wines and bizarre drugs.
When the cult had grown to the point that the army lost its discipline, the city was sacked by barbarians, and the cult leaders led the survivors underground.
When the characters find the pyramid in the desert, it is many generations later. The cult leaders rule an Undercity, and the populace work for them but spend most of their time in a waking dream state, living out vivid fantasies. It is implied that the cult leaders supply the populace with hallucinogenic drugs to control them. Resistance to the cult is maintained by three factions representing the original gods of the kingdom, each with a few fanatical adherents who apparently refuse to use the hallucinogenic drugs. The citizens are repeatedly referred to as being in a 'dream state' and the module describes for multiple encounters what fantasies they are enacting. References to actual drugs are more implicit than explicit (and it should be noted that Moldvay Basic was marketed to players of "Ages 10 and up").
The party initially finds the pyramid while seeking refuge from a sandstorm. Later, when they learn it is inhabited, they might encounter citizens in their (drugged) dream state, or the cultists, or the fanatic resistance. The party can just gather resources and leave the pyramid, but if they explore deeper they will be drawn further into the power struggle between the factions and eventually arrive at the Undercity.
If they decide to oppose the cultists, they can cure the populace of their drug-induced enslavement by exploring catacombs in which a rare flower grows that serves as an "antidote". They must win the flower from a mysterious guardian that could be one of the old gods.
Interested parties can explore my Campaign Journal for B4 here.