Lol, yeah that one time i mixed an "anti-histimine" (hydroxyzine) when i was already tipsy from 7 shots followed by 1mg of xanax and STILL wasn't as fucked up as i wanted to be, i just decided to take two hydroxyzine's (anti-hismines) and it did potentiate the xanax/alcohol to the point i was having a hard time of walking and had to lay my head down at the school library, and woke up to the cops forcing me to go in an ambulance to the hospital which resulted in going to a psych ward and a terrible time.
That was probably because mixing benzo's with alcohol isn't safe or good to do unless your dosages are in limit which mine were but the hydroxyzine just added to the extra sedation. Mixing anti-histamines to benzos alone will just increase sedation a little heavier head.