Hello! Thank you for the query. Vicodin is a narcotic drug, similar to Morphine. This group of medicines very often causes constipation. If you have been taking Vicoding for a long time, chronic constipation could cause all your symptoms. You need to know that intestine, when constipated, has no contact with the stool in some part of it (as the stool remains in other part). This part of intestine is empty and when suddenly the stool appears in it, it is not prepared for such situation. This gives a diarrhea. Other possible reason of your symptoms is large intestines issue. It can be inflammatory bowels disease or colon cancer. I suggest you to change Vicodin to some other drug if possible, and see if it will help. You should also visit your doctor have stool tests and consider colonoscopy. Hope this will help. Regards.