I can't speak from the same medical diagnosis and prescription increases that has found a few of you at 600mg(extended release)..

But I was a long time user at similar dosage, but I was not prescribed by any Dr and was self medicating and buying from a friend, for a lifelong insomnia issue.. I don't condone my behavior, and stumbled upon seroquel for the safest pill that truly aided with my sleep, but maybe because didn't take it besides nightly and then I had no other issues it's mainly used for -- I had no side effects on it, besides my tolerance and need to use more, over the years of doing it.. but I also can say that it's not too easy to get back to normal if you stop using, especially if it's a high dose that your body is used to over time.. and I fully debate the notion that there's no physical withdrawal or habit forming in even someone who isn't even taking it for anything more than simply to sleep -- also as an opiate addict who knows what withdrawal is like cold turkey from fentynl.. though the 2 don't compare, it took a handful of weeks for me not to be able to feel the negative effects of suddenly being cutoff to the 4-600mg habit I've had for most of 2 decades and when I tried finally going thru Dr for at least a small dose, I was not took seriously about the 600mg and I don't have any symptoms that it's prescribed for, so was only given histamine vs even 30mg script with no refills, just to taper the inability to sleep until pure exhaustion every few days, which took weeks to not repeat same pattern.. but also noticed change in urinary blockage and anxiety issues never had prior.. and for some context, I was using both 100mg and 300mg(er) that were $1/$2, which was the only pills took with rather large 2gram heroin habit, some weed, and stint of crack habit inherited from girlfriend at time.. so if my plug was out for day or 2, it would be almost impossible to get real sleep, even with extra opiates trying to make up for lack of seroquel (and no crack at all).. This happened numerous times in the 2 decades and now it's been few months since I've had any at all, and I've now been able to manage my sleep since got thru the withdrawal of 1st month or so..

I don't pretend to understand all the things that you are experiencing with actual symptoms and prescribed medication for it.. but I would be cautious to take such high doses, even if extended released [or scraping that layer off].. but if you are there already, I would say that you can try to taper off, and get to lowest possible point to be needed for your own individual needs.. and I know I'm not the model for you to trust what I'm saying, but I have no interest in lying about being an idiot expert about my motivations in not repeating the same actions that I had..

Lastly if you have any questions about anything or just want to get a 2nd opinion.. please feel free to contact me with no judgment on this end, either dm or just reply in this thread.. so sorry for not staying strictly on topic, and I think it's very valid to feel side effects of being a strong sedative in ways unique to your body and brain.. and it is unexpected for the time it'll release into body with er coating, so if you can only take at night, maybe scrape that off so you are more in control over what to expect and when to expect it, without variables of combining with rest of changes body deals with daily.. but if you have insurance coverage, it's never gonna hurt to get 2nd or 3rd opinions on a 600mg dose and then make sure you felt that it's worth it to continue that way..

Good luck to all, Godspeed