Nortriptyline
"I have had post-infectious IBS for about 9 months. I couldn't go to work, I couldn't eat, and I had severe abdominal cramping and diarrhea several times a day. I lost about 10lbs (I'm underweight to begin with, so this was troublesome). My gastroenterologist prescribed nortriptyline and Bentyl (Bentyl for intestine cramping, which I was able to stop taking once the nortriptyline kicked in), and I was back to nearly normal within a week. After several months of thinking I was healed, I stopped taking nortriptyline and my symptoms returned almost full-blown within a few days. Now I'm back on it and I feel fine again. I have had no side effects, except a little drowsiness when I take it (though I take it before bed, so it's not a problem)!"