Actually the Talwin/nx contains Pentazocine as the analgesic and Naloxone
(NOT Naltrexone). Even though Naloxone and Naltrexone are both opiate
antagonists, they do have VERY different durations of effect.
However as far as I am aware the Naloxone is included in the Talwin/nx
formulation in order to prevent or dissuade potential abuse of the drug by
attempting to inject it.
The amount of naloxone in the each tab is 0.5mg (I think) and there is not
antagonist effect when taken orally, as directed by your doctor.
Pentazocine itself is a partial agonist/antagonist itself, in that it is a
kappa antagonist and also a mu(1) agonist.

Now re: your question on "vicotyn"!!  I'll assume you really meant Vicodin.
Since this is just Hydrocodone + apap, and assuming that you are taking the
Talwin/nx orally, then I see no reason why the Vicodin would have no effect
(since the naloxone in the Talwin/nx is inactive when taken orally. However
it may well increase the overall analgesia which may well be a VERY
dangerous thing, depending on a whole range of things.
I must stress I am not a pharmacist but I do have an interest and some first
hand experience in the use of pain medications. I would advise that you
consult another medical opinion or at the very lest do a little more
research.
You could try the following sites for a start:
http://www.painconnection.org/cm/CMDisplayArticle.asp?ArticleId=154
or
http://www.drugs.com/xq/cfm/pageID_0/htm_d03676A1.htm/bn_Talwin%20NX/qx/index.htm

take care
Scoobs