Forever Thank Me Later Drake

ain't had a real buzz like this since the last time he overdosed

Eminem is comparing his overdosing on drugs to being in the rap game, he hasn't ODed in a while but he hasn't been in the rap game in a while either. now he is on a hit song, he is comparing that feeling to having a buzz from doing drugs.
Hmm in actuality a classic case of Schadenfreude--malicious joy over another's misfortune. Notice how fluidly the personal pronouns are used interchangeably. Listeners shouldn't assume that 'he' is the first-person 'I' where the piece begins.
This statement has a dual meaning. First that Eminem is feeling a buzz from this hit song. And second, that he had to be taken by ambulance because buzz is phonetically close to bus, which can also mean an ambulance.