I was on a very high dosage of Effexor XR for about a year. It caused me to have brain "zaps, shivvers" some shakiness of the hands, and just over all twitchy type problems that came and went. I hated Effexor though, and ended up quitting cold turkey and the withdrawal period took about a month to get over. If it gets to bad I would defiantly speak with your pdoc about it. Effexor has been starting to get a very bad rap as of late.

Good luck!