This song is the final step in Pink's (Roger Water's) transformation into the Neo-Nazi, fascist character you see in the movie The Wall
. Medics and the band manager come in and give Pink a shot to pull him out of his catatonic stupor, the manager pays protesting Meds some cash to shut up and let him take Pink to the concert in the state he's in (obviously a threat to his health, but the Meds, who probably don't make enough money, accept). In the movie Pink begins to melt on the way there, and underneath he finds that he is the cruel, fascist model of a Nazi party representative by the time he arrives at the concert. Supporting this, afterwards are the songs "The Show Must Go On" (Pink realizing as he gets to the show that there isn't really any turning back, and he's forced to go on-stage), "In the Flesh II" (the redone version of the first song on the album, now with Nazi-Pink singing, threatening random minorities), and "Run Like Hell
" (after the crowd, loving nazi-Pink, has been whipped into a frenzy, now hunting minorities in the street, much like late 1930 Germany). While it does seem that this is a song about the "joy of heroin," it has little, if any connection to heroin even if it's condition resembles that of somebody who's totally wasted.