OBJECTIVETo study the clinical effect of Tongxie Yaofang (TXYF) Granule in treating diarrhea-predominate irritable bowel syndrome (D-IBS) and its possible mechanism.

METHODSA total of 120 patients were assigned to two groups using stratified block randomization, 80 in the intervention group and 40 in the control group. To the intervention group the TXYF granule was given at one package each time, twice a day; the control group was treated with Miyarisan three times a day, two tablets each time. The course of treatment was 4 weeks for both groups. The total efficacy in them was compared, and data of scoring on stool (Bristol method), abdominal pain, abdominal distension, and mental condition were collected before treatment and 2 and 4 weeks after treatment. The activation of mast cells (MCs) of six patients chosen from each group was detected as well before and after treatment.

RESULTSNo significant difference between the two groups in terms of the total efficacy or the scores of symptoms before and after treatment was found (P>0.05). The number of activated MCs was decreased in the intervention group after treatment, showing significant difference as compared with that before treatment as well as with that in the control group after treatment (P<0.01).

CONCLUSIONSTXYF is an effective preparation for the treatment of D-IBS. It can quickly lessen abdominal pain and distention, improve the property of stool, and improve mental tension and depression in patients. Its mechanism of action might be through the adjustment of MCs activation to decrease visceral hypersensitivity.