I have at times in my life been a daily user of DXM for extended periods of time. And tripped at least once a week from like 2013 until probably March or April of 2022, so nearly a decade. I know there are plenty of people who have taken it further, but I would consider myself a (at least one time) heavy user of DXM. At the beginning my doses were closer to the 500mg-600mg range, for a period probably hit over 1000mg regularly and then the last couple years of use I would pretty much always take 900mg every time. Though, do keep in mind my tolerance was, and is, insane.
I have not had any major health problems due to my use. I do believe that at one point I had an ulcer from eating such large amounts of pills on a regular basis. I actually suspect this is a common issue among heavy DXM users, just myself I've known three people who have had to have surgery to repair ulcers in their late 20s or early 30s and were also heavy DXM users. While this isn't specific to DXM, I suspect eating any pill in this amount and frequency would fuck up your stomach, I is worth mentioning.
My doctor runs blood tests twice a year on me and at one point during a heavy period of use my liver enzymes were elevated. I can't confirm this was because of DXM, but by the next time I was tested I had mostly stopped using DXM and my liver enzymes returned to normal.
Mentally, it's kind of hard to really quantify, what, if any (and I assume there is some) cognitive effects there've been. I was forgetful, clumsy, spacey years before I touched drugs. Am I still those things? 100%. Are they worse? It's so hard to tell, y'know?
One side effect I do get from DXM is urinary retention. Again, nothing I have confirmed or can say for certain, but there does seem to be some hesitancy with urination that was definitely not there before I abused dissociatives so heavily. (To be entirely fair though, I also was using numerous dissociative RCs during this period, as well as ketamine, so if there is any damage or effect there, it could be from that.)
The effects of DXM have changed over time, which I imagine is probably what a lot of people are talking about when they say that DXM "stops working" for them. I still enjoy the effects, but it's a lot different from when I first started.
Oh, I would also occasionally use CCCs. I know they're bad and you shouldn't and I'm not encouraging their use at all, but relevant imo, when I was regularly tripping on CCCs I had a much more significant cognitive decline. After I gave up the CCCs, that went away.
That's...pretty much any and all side effects that I can think of that I could possibly ascribe to DXM use. I won't say whether I think it's "safe" or not, but you can draw your own conclusions on that. I may think of another random thing or two and will update this post if so, but I believe I hit all of them.
Edit: Oh, not a side effect of use, but maybe a story that may help illustrate how dangerous, or not, DXM is. The discussion on pure DXM powder made me think of it haha. Basically I imported 100g a number of years ago and I was hitting it hard. Taking gram doses 1-2 times a night, every night. After nearly a week of this, I blacked out one night (as I was prone to doing at the time) and came to the following morning tripping harder than I've ever tripped. I looked at the bag and it was noticeably lighter, though the exact amount of DXM I redosed after my initial gram is hard to say. I felt like I was dying and was freaking out. I calmed myself down and decided to take a Seroquel to try and force myself to get some sleep and sleep it off. Got up long enough to tell my family I wasn't feeling well, popped 200mg of Seroquel and went back to bed. Slept 24 hours and I woke up tripping just as hard. I couldn't keep hiding in my room and quite frankly I was legitimately scared, so I told my grandmother what had happened and we went to the ER. They ran my bloodwork and checked me over and said that nothing was medically wrong with me. Knowing that much, I felt much more at ease and the remainder of the trip wasn't so bad but still lasted for far too long. After the hospital I was tripping for another week and then had an intense DXM afterglow that lasted another week or so. It spooked me, that was actually a defining moment in my life that made me stop being so self-destructive and reckless with drugs, but I was physically fine.
