Namaste,
I recall answering a similar question yesterday, although I'm not sure who posted it and I didn't go back and research it.
My answer to your post however, is that the palpitations are caused by your anxiety and/or panic attacks and not from the medications themselves, unless, perhaps you have a pre-existing heart condition of some type.
Michael
xanax works fast and can last for up to five hours. the paxil is an antidepressant which takes afew weeks to get in your systom, after its in your systom you should start to feel better.
wish you all the best
and god bless