codeine causes a rather large release of histamine from mast cells compared to other opioids, and has a comparatively weak narcotic effect. injection via intracenous route can lead to a humongous histamine release, pulmonary edema, basically anaphylactic shock. this is something i have read out of medical textbooks and never had the desire to verify. (the books usually say IM injection is the only way to go - because it diffuses slowly into the blood). by this extention i suppose you could plug codeine, but since it needs liver metabolism, oral is really the best route.
really I am not going to dispute this a whole lot. If you want to smoke or IV codeine on its own, be my guest, but do be warned!
codeine 6-glucuronide is made... in the liver, by udp-glucuronyl transferases. so you still need to move codeine through the liver for it to become active. smoking it on its own is a waste of codeine at best and a health risk at worst
if you have cold-water extracted codeine, it is not pure in the slightest, esp. if it is from tylenol 1's. how exactly you extracted this codeine and how you know it's pure would be a good story to hear.
if what you have is a salt you can't smoke it anyway, it will just burn and decompose, it has to be a freebase for effective vapourisation.
