Zombification through Subtances

I'm just about to sign out of my dorm for spring break and I cannot help but think how break just gives college students an excuse to party excessively. From what I have heard, the majority of my friends all plan on spending the break partying and getting trashed. Earlier this semester I mentioned that you could call a "drunken idiot" a zombie. After thinking about that, I realize I was just dehumanizing anyone who goes to a party, which is quite a common thing to do (attending a party, not calling them zombies). At parties, people blame whatever substance they take for whatever actions they do as a way to justify them. According to that argument, every action a person takes is not their decision, if they go to a party. I believe this argument is flawed because even when a party-goer is under the influence of something, it is possible for them to have control of their mind and have coherent thoughts. I wouldn't know from my experience how much bath salts affect the human brain so I'm not completely sure how much control Eugene had. This still makes me wonder if he really had lost all of his control. Would being under the influence really cause a person to lose all of their humane ideals? Do such substances really take away all the things that make us human? Does being under the influence cause one to become a zombie?