It's easy to get confused, especially if you see that the actual name of hydrocodone is dihydrocodeinone.
Anyway, like mentioned dihydrocodeine is, I believe (and I am no chemist), 2 codeine molecules attached by a water molecule. Likewise, the strength is approximately that of 2x the mass of codeine i.e. 30mg of DHC = 60mg of Codeine, but otherwise it is very similar. Like codeine it works by being converted into an active form in the liver (dihydromorphone). Also, I have seen it written here (doesn't make it true, but it was a fairly reliable poster) that DHC is unusual in that it is not a central nervous system depressant.
All in all, it is a very effective pain reliever but it is becoming more and more hard to find due to a crackdown in Europe.
If you have more questions, feel free to PM me.
take care,
daddyj
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Misty morning, clouds in the sky
Without warning, the wizard walks by
Casting his shadow, weaving his spell
Funny clothes, tinkling bell