My brain always feels healthier after 600mg of DXM too!
Also in regards to DXM feeling like eating ink and plastic; I have been abusing DXM for about 8 years now. Since I was 14. The frequency definitely died down after I turned 20. I used to binge for days and days. At one point I had 25g of USP grade DXM powder and dosed for 6 days straight, it had built to such high levels that i remained fried for the next day until I mistakenly puffed on some dank bud and it sent me into a full blown sigma psychosis. I had one other incident where i accidentally dosed too many days in a row and ended up in plateau sigma. Not fun at all and Sigma will leave your brain filling like it has just been slow-cooked.
I always wonder what is happening to my body when I dump 12oz of tussin into it. UGh... I used to be able to handle syrup. FOr years i could chug it down with no problem. no GI problems whatsoever. When i turned 18 my stomach started rejected the stuff, EVEN THE PURE POWDER! it was DXM not just the syrup. But after a while i started to be able to handle it. Like now i can chug the shit again and stomach it but when my body starts to break it down my GI has a terrible time with it. I get bloated and gassy and have nasty tussin runs that just ruins the whole experience. You can hear my stomach making loud weird gurgling noises and shit.
Hope my liver and kidneys and pancreas are ok. Diabetes runs in the family. All that corn syrup and menthol and gunk just does not sound good. I've drank maybe 15 gallons of cough syrup in my lifetime. thats just syrup.
Sorry for getting off topic. You will be fine. I fried my brain twice on DXM and had complete psychotic breaks that ended in hospitalization. SO long as you are not dosing 1-2x a day for at least 3 days then you should be good. IME DXM will accumulate if taken consecutively like i did. If i remember correctly DXM interferes with its own metabolism. I think DXO inhibits CYP2D6 somewhat. Its been a while since i've read White's faq.
Also I want to add that I am fine cognitively and emotionally. I have had pre-exsting conditions that the DXM made worse. I had minor cognitive issues for about 3 months after my psychotic breaks but that is because i was stupid and dosing like a fucking madman. and even then it was only affecting my speech as in trying to form sentences and get my thoughts out verbally. I am in college and am a great father and boyfriend.