Hey friends, i am aware this original post is a bit outdated, but I thought I'd follow up with a comment that may be useful to others reading, and, if the original poster is still active and in this situation, hopefully it'd be useful to him or her. (though I'm assuming he/she figured out their own solution by now).
I'm not venturing to suggest this, but it seems pregnenolone can be used safely for many people, and, if I recall correctly, it had some gaba-b ergic antagonism, so it might be that if you used that during your off time (the time that you don't need phenibut's effects, if there is such a time) , maybe it would upregulate gaba-b receptors. This is just an idea, you might want to check if there's any research about it... even if you have to go to the extent of finding out: how significantly does pregnenolone antagonize gaba a&b receptors? The next thing you'd want to research is: information about gaba-b or gaba antagonists that have shown to upregulate receptors at the same or similar potency as pregnenoline, and, the safety of such a thing.
I do suggest the following, based on experience: your body will adapt to having a lower dose even if you have to suffer in between. Taper down and I am sure your body will eventually figure out how to respond appropriately . if it doesn't, consider quitting if possible and then re-starting at a later date on a lower dosage.
My anecdote: funnily enough, with some experimentation this year, it seems that, on the days where I combine etizolam and phenibut for sleep, when I take the higher dose it actually causes more tolerance problems or less therepeutic effect. For example, it seems more favorable that I am on 5 mg etizolam and 500 mg phenibut, whereas if I boost it to 7.5 mg and 750 mg/ 1 g respectively, the particular therepeutic effect I'm seeking is lost (mine is for insomnia). However the anti-anxiety effects still extend to my benefit which is great.
I think your pregabalin dose is way too high. There was a time that I took something between 3g-15 g a day. I know, ridiculous. This was several years ago. I swear it had some permanent effect on my brain, worsening insomnia, unless maybe it was something else I was using at that time. But, that being said, the reason for you only feeling side effects could be owed to more than one thing:
1) the dosage is too high. 4 grams is a ridiculous amount especially daily (me assuming the worst case scenario).
2) the source or form of your phenibut. years ago I got a bunch of side effects from phenibut that I don't get at all now. Perhaps this is owed to source and form (HCL vs free amino acid; LiftMode vs Purebulk) (yeah, purebulk once had it, I actually emailed them years ago saying the stuff was harmful and now they don't sell it anymore, I always wonder if my comment contributed to that, haha, good move for them though considering this is not a nutrient or a natural health product). .
Plenty of anecdotes on the internet that Kava Kava rapidly reverses Phenibut tolerance, anybody here had success? My own experimentations are quite mixed, not sure yet if it in fact works.
Also, what about Homotaurine?
I've never tried combining Kava and Phenibut, though i really dislike kava. If your results are mixed, who knows, maybe that could indicate that it has an inconsistent effect, either that or maybe placebo. I think the best option would likely be, as suggested above, remove tolerance by suffering for some time on a lower dose and regaining tolerance so that it is effective again. And of course, again if you are using it daily, or multiple times a day, there is the option of lowering the frequency of dose and your body will likely adapt to those changes until you feel like phenibut is doing what it is supposed to do without requiring more.
I'm guessing with these things that there is some "minimum/maximum effective dose" for people. in my personal experience it seems that substances like these have a sweet-spot with both dosage and frequency of dosing, which, if insufficiently reached and if exceeded, does not work in the expected manner and causes trouble.