I have been taking lomotil for over two years, as prescribed by my gastroenterologist for chronic diarrhea due to irritable bowel syndrome. What I have found is that it does not prevent you from having diarrhea episodes, but it will prevent them from being less severe when you do have them. It is slightly stronger than immodium, but not a whole lot. Taking them together has not helped me much in the past. It seems like when I am going to have diarrhea, nothing can stop it completely. One thing I have noticed is that it does make me both dizzy and drowsy, especially if I take more than one a day, so it is not a good idea for me to take it before driving a car or going to work. Some people can also take it everyday preventively, but I do not want to do this and be in a dizzy drowsy daze when I do not have absolutely need to take the medicine. I wish there were a medicine out there that could totally eliminate diarrhea episodes, especially if taken at the first onset, but until then I will continue to use the lomotil.