What drug does Usher's condition remind the Narrator of?

Sorry, this took me awhile. The drug is opium.

"His voice varied rapidly from a tremulous indecision (when the animal spirits seemed utterly in abeyance) to that species of energetic concision—that abrupt, weighty, unhurried, and hollow-sounding enunciation—that leaden, self balanced and perfectly modulated guttural utterance, which may be observed in the lost drunkard, or the irreclaimable eater of opium, during the periods of his most intense excitement."

In the introduction of the story how does the imagery depicted in the beginning of the story of the fall of the house of usher contribute or set up the story consider what the house symbolizes