In hindsight, I had also been taking pramiracetam regularly, so perhaps this was the cause? I recall reading somewhere that nootropics increase expression of NDMA receptors following regular use. Because of this NMDA antagonists understandably will have a weaker effect or will require higher dosages...I suppose?
Pram being a fairly strong AMPAkine, especially in comparison to the more common racetams, it'll significantly diminish the effects of dissociatives. Have you been taking MXE and Pramiracetam at the same time? If so, then you have almost no tolerance - I made the same mistake myself when using IDRA-21 with DXM, tricking myself into believing I had a massive tolerance, and my lack of forethought (and afterthought as well, for that matter) cost me gravely. If this is indeed the case, just avoid taking any Pramiracetam for at least 3 days before using MXE and you should be fine. If this isn't the case, then I'm stumped. There's no pharmacological reason I could think of for two almost entirely unrelated substances causing cross-tolerance with each other. Science hasn't come to a point where we could give a definitive answer explaining something like this, were it to be true. Given that I've used dextroamphetamine and other weaker stimulants very often in my regime along with MXE without encountering any of the issues you've brought up, I can almost guarantee you the pramiracetam is the root of your "tolerance." Again, stop taking Pram a few days before dosing MXE and you can thank me when your "tolerance" magically disappears.
Mildly OT: On another note, I've been having a bit of a thought lately. I haven't done any research to confirm my theory at this point, but given the ability for AMPAkines to diminish or completely eliminate the effects of dissociatives, I can't help but wonder if they might just be the only substances with the ability to reverse tolerance to dissociatives? If anyone with some noticeable level of tolerance for a dissociative (any dissociative, it doesn't matter) would like to give this a shot, taking AMPAkines religiously on off days in an attempt to reset or, at the very least, halt the continued development of tolerance, I'd greatly appreciate the effort. The racetams may not be the best choice here, despite being more common, cheaper, and better studied compared to their cousins - I feel their potency as AMPAkines, with the possible exception of Coluracetam, isn't quite at the level needed for this to work. While Piracetam did significantly diminish the effects of DXM in my experience, IDRA-21 almost completely wiped out the effects despite having used multiple substances to massively potentiate the DXM. I wouldn't use Sunifiram either due to the possibility of potentiating dissociatives (while we do know this happens with stimulants, I can't say for certain whether or not Sunifiram would potentiate dissociatives as well), an effect which might be confused for a reversal in tolerance only to slowly diminish over time. Unifiram and IDRA-21 would probably be ideal for this type of experiment. Any takers? As soon as my MXE tolerance reaches a significant level (most likely, I'll start once 300mg is required in order to hole), I'll be sure to go crazy with RC nootropics again. For now, PRL 8-53 and Coluracetam are the only "non-conventional" nootropic substances I'll be using, as I'm broke and I've recently run out of my supply of IDRA-21. Sorry to high-jack your thread Afer, although this thought does have some relevance to the topic at hand, albeit a somewhat loose resemblance. If anyone is interested in discussing the theoretical potential for AMPAkines in reducing/inhibiting the development of tolerance to NMDA antagonists, or has some relevant experience to share on the matter, I'd be very interested to hear from you. Please feel free to send me a PM, so as to avoid going even further off-topic here.
Be sure to reply back and fill us in on your results, Afer. Though as I said before, the Pramiracetam is almost definitely the culprit here, I'd be even more interested to be wrong. Good luck, mate. It'd be quite a shame not to be able to experience the full spectrum of such a wonderful substance due to some silly little error like this. I can't say enough how much I love this drug. I hope this post proves to be helpful for you.
And, on another entirely off-topic note: Solipsis, do you mind clearing out your inbox? Unfortunately, my PM didn't seem to go through. Thanks.