I was taking 1-2 500mg. tablets of Vicodin daily for a couple of months. Took it as needed rather than on a schedule. Last week I was down to 1/2 -1 pill just as needed, probably every other day or two. One week ago, I began experiencing pretty severe palpitations, and they haven't quit since. I have been in the ER thinking I might be having a cardiac event because I was sweating and having shortness of breath as well as some nausea and severe indigestion. I checked out just fine, and am wondering if the sudden withdrawal from vicodin might be the cause. There has been no reduction in symptoms since they began 7 days ago.