A lower end oral dose of MXE (~30mg, as I have a decent [possibly permanent] tolerance to it) potenciates kratom by quite a bit. Oral MXE on it's own generally feels very narcotic to me, very removed from it's psychedelic/dissasotiative nature as opposed to other ROAs.
I should note that I take 4-6 grams of piracetam a day as well, which seems to take away from most of the effects of MXE. I'm reading the link to this ADD thread in a few minutes:
http://www.bluelight.ru/vb/threads/529450-Opiates-and-Piracetam. Not sure what the conclusion is on that yet, as it seems like piracetam could either potentiate or dull the opiate/opioid experience, ergo the kratom experience. In regards to the kratom high, I'm just assuming with that, as it produces opiate/oid-like effects.
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All this aside, one should be mindful not to go overboard and get addicted to two powerful substances. It would be very easy to become a slave to both.