RESUMEN
IBS is the most common disorder diagnosed by gastroenterologists, which is seen in approximately 40-50% of patients seeking care from a specialist. Several randomized controlled trials, have assessed the therapeutic effect of anti-depressant drugs, but there is not enough evidence to prove their effectiveness. Fifty cases meeting Rome II criteria for IBS with predominance of pain and diarrhea were included in this study. Organic causes were ruled out by detailed history, physical examination, laboratory tests, small bowel transit and rectosigmoidoscopy. Participants were then randomly assigned to receive either Amitriptyline or placebo. Subjects were followed using a simple symptom score system before, after 1 and 2 months of treatment. At the end of the 2nd month, Amitriptyline showed more influence in reduction of flatulence, mucus passing and incomplete defication feeling, than placebo [p<0.05]. Also, symptoms general improvement rate was 39% and 15% in Amitriptyline and placebo groups respectively [p<0.001].The rate of side-effects in the two groups did not have significant differences [p>0.05]. Amitriptyline is an effective and well-tolerated treatment for pain and diarrhea predominant IBS