Codeine conversion to hydomorphone

[ironmics]

I was looking through wikipedia about codeine randomly and read something I found interesting.

"Roughly 5-10% of codeine will be converted to morphine, with the remainder either free, conjugated to form codeine-6-glucuronide (~70%), or converted to norcodeine (~10%) and hydromorphone (~1%)."

1% conversion to hydromorphone would seem to me that the hydromorphone could be active. It also seems like one would have 100% availability to this 1%. I can not find how hydromorphone is made in vivo though. Does anyone know anything about this? I have not been able to find anything relating to it. It would also be interesting to see what effects different enzyme inducers/inhibitors have on the formation of it.