I just checked SAMF and its under analgesics:
Tramadol: is an atypical opioid structurally akin to tilidine. It falls under other opiates... not Benzomorphan derivatives.(But that is right next to it so probably very close)
What edition samf was this?
Benzomorphans are opitate derivates ... they are synthetic opiates BTW.
They are antagonist-agonist drugs that work on the opiate receptors. A closely related drug to the family is phenazocine. These substances are derived synthetically from the morphine structure. Tramadol is a drug that does this hence why its grouped with them (lippinocotts illustrated pharmacology groups them according to activity and tramdol is grouped with the benzomorphan group but they
are all opiate analgesics).
tramadol structure:
http://structures.wishartlab.com/molecules/DB00193/image.png
now tramadol in the capsule you take it is as racemic mixture, basically meaning its mirrored chemically in structure. So it can be dificult to see its similarities, but if you look carefully you can see its relation to the morphian family which benzomorphans are a part of. Now because the nature of how trmadol is prepared if you go hunting for its structure you going to find many different looking pictures but they are isomers (S and R)
Phenazocine (a true benzomorphan): structure:
http://forendex.southernforensic.org/C/dl58.png
or use wikipedia for a bigger picture (lol)
http://upload.wikimedia.org/wikipedia/commons/d/dc/Phenazocine.png
Now the key is the nitrogen when identifying opioids, that makes what is known as ring E if its disturbed there is no activity in the opioid at all, so it must be present in the ring system. Its the bridge that allows the compound to interact with opiate receptors (I call it a bridge I forgot whats its proper name is. Makes life easier to know its bold notation when drawing it) that bridge relation to the nitrogen is key.
this is how to make a benzomorphan: (I dont have a scanner, ok lies i do im too lazy to scan

)
And as I said earlier
RiaX said:
If you really want to know, then you have to look at its chemical structure to see why its classified as a benzomorphan. It belongs to that family of drugs even though its not a direct member its a cousin per say. Its one of those dual action drugs that works on a series of pathways from opioid to actylcholine receptors and many more.
Its activity is comparable to codiene in other words similar to that of a low ceiling opioid if you look at its structure you can see the basic structure of an opioid as well.
Anyways I didnt classify it, thats just how its classified in text.
and
RiaX said:
its a synthetic miscellaneous compound... The SAMF defines is under the benzomorphans
So unless my SAMF is out of date and its suddendly changed into a proper opioid (like morphine) then maybe I should go shopping for a new samf
though I doubt tramadol has changed its structure and my SAMF is pretty new, was planning to buy the newer one this week anyways. So as I said tramadol is a benzomorphan .... but not a true one but a cousin

that my lecture for the day.... phew okes are keeping me sharp in academic knowledge here D: