That's no good

How much did you take roughly?
Are you on any meds like effexor? Combine it with anything?
Might not have been ethylphenidate.
No it was pretty terrifying actually. I took about 80mg orally. I get a slight euphoric feeling for about 30 minutes, then this sense of doom, almost felt like my brain was very overstimulated (tested heart rate, was around mid 80's, so relatively low given the use of a stimulant), but felt like a storm. I then went on to feel like I could have had a seizure at any point for the next 4 or so hours, all the while anxiety was building. This subsided after about 5 hours of dosing, but had to walk slowly as I had a heart palpation (I'm in good health - so this should never happen), but otherwise no other cardiovascular issues were noted. However, after the initial 30 minutes of slight euphoria, my mood progressively decreased through to dysphoria, then depression after a few hours and stayed low for around 8-12 hours (it got so bad that I was thinking of taking my SSRI again (I'm coming off these, see below) - and would have done if I didn't think it could have lead to a potentially dodgy reaction). The mood has improved greatly since fortunately. Effects lasted over 12 hours - was still feeling overstimulated at 3 am this morning! (Took the EPH at around 1 pm).
I was taking an SSRI, which was Sertraline (Zoloft/Lustral), at 50 mg every 3 or so days, but stopped taking it about a month ago.
The idea that it wasn't Ethylphenidate did cross my mind, but got it from a reasonably reliable vendor, and the effects seem consistent-ish with some others experiences (though the negatives GREATLY outweighed the positives in my case). I couldn't find much dose data save for the fact it is 1/4 as potent as Methylphenidate (so would have been equivalent to 20mg or so of MPH, and most trip reports relate to doses in the 100-200mg range), but may have overdosed.
That said, I really don't like Coke much (low and comedown far greater than the high), which works in a similar way apparently, so maybe my brain doesn't like those kinds of stimulants (have no issue with Amphetamine or MPA). All I will say is that this stuff felt way more dangerous than Coke. Be careful with this stuff.