Oxycodone is already, IME, one of the most sedating opiates, even more than Morphine for me.
Promethazine, honestly, when used in the gross amounts as contained in "lean" (cod/prometh) is not really easy on the body. Nor pleasurable, nor does it add to the opiate " buzz" or w//e unless you want to be asleep.
I won't judge, I drank a lot, as a kid, But lil' wayne is a dumbass for pushing that shit, rappers are stupid for drinking it, and the American media/government is fucking stupid for lying to everybody abuot the dangers of particular medicatons.
^ And NO technically, promethazine is NOT a sedative, but practically, it fucking IS a sedative, because after drinking 4 oz of lean not even 40mg of Adderall would keep me up, and that's with a high codeine tolerance, and low amphetamine tolerance.
Now I haven't touched lean in YEARS lol, that horse shit, i'd rather suffer Withdrawal now honestly, my tolerance to opiates are so high the promethazine would have me out long before I got anything from the codeine.
TLDR; Be a man (or woman), take your pills like an adult, they'll probably feel even better WITHOUT the sedetave(promethazine, or soma, or benzos all just water down, and muddy the opiate feeling.IMHO).
WARNING; using opiates WITHOUT ridiculous amounts of sedatives may be waaay more addictive, since you actually might get up and do stuff, and you can get used to doing just about ANYTHING on opiates pretty quick.
P.S. you can always add, but you cant take away