I mean, I overdosed on F. Your survival instinct will surely kick in fast enough for it to be a problem - I'd say I had about 3 or 5 minutes before I became incoherent and passed out. I wouldn't say that I felt "high" during that time though - it was just that I could feel my vision, focus, and balance fading. There's definitely a chance you will panic - but if you wait long enough you might not be able to read to make a phone call anyways... definitely panic inducing.
I walked to my desk after absorbing the f and then while typing on my notepad I had worse and worse ability to focus until I just passed out. Apparently I kept typing for a bit longer than i remember LOL. It was all gibberish typing though...
You don't die instantly either. I was unconscious for 8 hours or so before I was given narcan and hospitalized.
I have catatonia/dystonia and ocd now because of the injury it did to my brain.
I only threw up after they narcand me