Well, alcohol and some medications can cause peripheral neuropathy, which means they can destroy your autonomic nerves.
I don't know about Xanax, and it wasn't on the MedHelp list of possible causes. The best way to find out is probably to talk to your pharmacist and ask if Xanax can cause peripheral neuropathy. If that doesn't work, call the manufacturer of Xanax and ask if there are any risks or incidences of Xanax causing peripheral neuropathy.
I suspected feverfew taken in high prescription dose for causing trouble with me. My internist at the time when I had been taking it and was noticing more trouble said there was a potential side effect to feverfew, irreversible I think he said, where the blood vessels remain flacid and don't contract with standing like they are supposed to. But I don't think that permanent thing happened to me, because my BP definitely can go up with standing,