Codeine and first pass metabolism

[kleinerkiffer]

I have a few questions regarding codeine and first pass metabolism in general.
Codeine needs to get metabolized to Morphine and some other metabolites , right?
Does this metabolism happen during first pass metabolism or is first pass metabolism destroying some of the codeine?

" First pass metabolism can mean that the prodrug gets converted to the active metabolite by the liver, after absorption in the stomach and intestine into the blood stream. when you take the prodrug oral, everything will go to the liver, but if you take the prodrug rectal some of it will go into the venae cavae (this is the small part you lose) and most of it will go into the portal venous system, we're it will travel to the liver and gets metabolized.
But there are other prodrugs that will be destroyed by the liver and get metabolized after passing the blood brain barrier for example."
Am I right, or did I misunderstood some things?
Can you explain it a bit more?
Thanks for answering

 

[aced126]

Unlike in other routes of administration, when you take a drug orally, it goes to the small intestines. From there it gets absorbed into a blood vessel called the hepatic portal vein, which transports it directly to the liver for metabolism.

Thus in the case of codeine, it is a good idea to take it orally so that a lot of it can reach the liver.

 

[clubcard]

Some members of this class - 14-methoxy DHC have very strong activity themselves. The methyl ether just a hydrogen-bond acceptor blocked. Look at oxycodone,