I was on eleuthero for about 8-9 months, with a few weekend breaks here and there. Felt pretty good on it, and it definitely increased my strength and endurance. But I ran out about 3 months ago and decided to take a longer break, and then I severely crashed after a few days! Swollen glands, chills, flui-sh feeling really bad for a night, curled up in a chair in agony, etc. then that mostly went away the next day just leaving the worse fatigue. I've been severely crashed since then, though, with my heart pounding all the time and a kind of oxygen hunger, along with a lot less endurance and more pain everywhere. Not sure what it did!
My naturopath said I taxed the adrenals while I was on it, since my endurance was better while I was taking it and I was doing more things. But I'm not sure I totally buy that, because I felt as good at the end of the 9 months as in the beginning, if not better, and if the adrenals were getting wiped, I'd expect to have gone gradually (or quickly) downhill. But I only felt worse after the crash, with not much improvement since then. I think the eleuthero alters norepinephrine brain chemistry in certain ways, which contributes to the anti-fatigue effects, but then withdrawing it too suddenly caused some kind of neuro-immune adrenal crash.
I had basic blood tests a few weeks ago, and everything was totally normal, except thyroid was a little worse (TSH up, T4 a little down, both within "normal" range, though). So I'm not really sure what to do except add it back again and see if it will fix whatever "broke" when I went off it. I've already been taking about 1/3 capsule a day just to feel a little better, which seems to work. But I have the concern that now that I'm weaker, adding a full dose again WILL wipe out the adrenals more. Very frustrating to have this kind of setback. :- (
Anyway, posting just to share my experience, to get advice if anyone has any, but also as a caution for those who want to try eleuthero not to go off it cold turkey! I think if I tapered like every other day for a while, then half a cap every day, etc. I might not have crashed.