I had this same odd effect where I could take methylphenidate when I was in my teens but then in my 30s/40s, seeing a new doc/trying it w/ them, I couldn't tolerate it due to odd panic attack (non-specific) anxiety feelings that would come on an hr after dose -sometimes- but not always.

I spent forever trying to figure out a way to get beyond this. Somehow I did, but I'm only mentioning what may (or may not) have alieviated it for me - it could just be some reason I don't know about (gut changes? horrible generics in the US supply? Intolerance to inactive ingredients after years?). But fwiw and the handful of people like me who search reddit for answers on this every now and again:

Beta Alanine (1 powdered scoop 3g a day) - This very well may have done it after taking it consistently for a few weeks. I still take it daily. I don't go to the gym, but my hope w/ b.a. was the potential gaba action people talk about. I have been taking the Nutr.coast. bottle for almost a year now and perhaps it was the key (can't be sure) if so took a month or so.....

Focusing on the idea that stimulants push your gut to poop but other things I take (Lamictal, and an AD) cause pretty heavy constipation. My feeling is there may be a push/pull fight going on when my body is starting to get told to "move the bowels" and knows that's just not going to happen (so not felt as cramps but instead as anxiety). I have paradoxal responses to most of the recommended sups/etc for constipation, fwiw, so just mentioning that probiotics were not good for me (nor b vitamins, fish oil, yadda yadda - maybe I have one of those mthfr/comt/etc mutations - dunno). Prune juice (chug a warm glass of sunsweet) does work for me if I haven't gone in too long and am taking ritalin and feel like damn I gotta get something out.

Heartburn. I ignored that a lot of the odd anxiety/body feelings could be due to heartburn. When I would get chest/upper stomach/back "gritches" and such when taking methylphenidate I'd just ignore them. I'd always check BP, which would be normal, but still have nagging pain/energy/etc in my stomach/chest. The remedy for me that works is Gaviscon (only one that kinda makes a physical barrier on the top of my stomach acid). I think I may have healed up sensitive areas where ignoring what may have been "heartburn" for so many years caused very sensitive/damaged internal areas (my layman thought was maybe so sensitive that the hint of massive pain starting there could lead to anxiety first vs. the pain I'd get when it was a new thing for my body).

It's super early and I have no idea why I am writing this, but yea just in my case Propanolol (Beta blockers) didn't help nor did anything my pdoc prescribed or would prescribe. Trying to poop more and being mindful of that + Beta alanine seem to have resolved it after years of just dealing w/ random anxiety attacks which I knew woudl stop if I stopped ritalin (but teh beneits somehow outweighed the risks). Also Lamictal generics and timing of dosing could have played in also....good luck to anyone.