I've noticed seizure-like symptoms (and a vibrating/buzzing sensation in the extremities) on samples which ended up not being MXE. No real idea on what the substance was but the theory at the time was that it was most likely tiletamine. Dysphoria is pretty well documented with tiletamine.
A theory about the weird posturing some of you have experienced is that it may play on the brain in a similar way that schizophrenia affects the body.
MXE causes temporary 'toxicity' to the cerebelum,
and many of the odd physical symptoms associated with schizophrenia are mediated by damage to the cerebelum.
Personally, I have not experienced any of that stuff with 'pure' samples of MXE.
My favorite route of taking the drug has been through I.V. and I have noticed a weird effect!
To preface: I have built up a ridiculous tolerance, requiring about 50-75mg I.V. for decent effect. The rush is intense and the effects subside after about one hour. I redose maybe 2-3 times and then call it quits for the day. After effects last about 6 hours and then I can sleep with some grogginess.
However, after the 2nd re-dose I sometimes slip into a traditional K-hole type space but when I re-enter I'll be completely sober. I've experienced this when using DMT and MXE in the past and it is always such a conundrum. I can go from holing insanely hard to stone-cold sober, albeit with a bit of residual stimulation.
Normally I can't walk real well or talk without slurring after emerging from that space, but the times like I mentioned, I will be able to hold a fluid and normal conversation.
I have no idea what causes this.
I do know that I often feel pressure around my head in a coronal pattern. Imagine the feeling of having a pair of sunglasses on your head, but in a circle on the scalp like a crown. Like I'm wearing a fuzzy crown. This effect is usually about as lasting as the residual stimulation with decreasing intensity.
Pretty sure none of this is great for my brain so I'm planning a move to memantine eventually. When I was using MXE heavily in the past, memantine lasted twice as long but I could sleep on it and had no desire to re-dose. I think for those who experience a heavy NMDA antagonist tolerance, memantine should be your next drug to try. It's on par with the price of MXE anyway.