I’ve also noticed that kratom has a super strong binding affinity to the mu receptor site- it took 3 goes with diacetyl (tar) before breaking through to euphoria. I just the other day, got a script for 30x Tylenol 3’s and I started with x2 and felt nothing, went up to 3 and still feel nothing. I’m sitting here contemplating taking x4 ( which would be 120mg) hoping 1.2g of acetominophen is ok. I don’t have much experience with high doses of Tylenol…
Anyhow, I believe it’s my evening dose of kratom to get enough pain relief to sleep at night, that is blocking my receptors from codeine even eventually making it to my cyp2d6.
I dunno tho, had a buddy synthesize a few lbs of tramadol for me in the early 2000’s and enjoyed it immensely for almost 10 years - so I’m sure my cyp’s are 6in’ it right…