RESUMEN
BACKGROUND AND AIM: Irritable Bowel Syndrome (IBS) is the most common gastrointestinal dysfunction characterized by abdominal pain or discomfort, as well as changes in bowel movements and stool shape. Given the global trend towards the increased use of complementary and alternative medicine (CAM), the high prevalence of IBS, the lack of a standard treatment for all IBS subtypes, and patients' willingness to use CAM treatments, investigations into CAM treatments are needed. Accordingly, the present study aimed to investigate the effect of a mix of two herbal medicines (Zataria-Trachyspermum, ZT) on the clinical symptoms of patients with IBS. EXPERIMENTAL PROCEDURE: The present study was performed on 3 groups including the positive control, experimental, and placebo groups. The sample size was calculated as 150 participants. Fifty patients were assigned to one of three parallel groups (ZT capsule, placebo, and mebeverine capsule) by block randomization. All three groups were treated for 4 weeks. The patients were monitored in the follow-up stage for 2 additional weeks. RESULTS: After the fourth week of intervention, symptoms of pain, bloating, and reflux showed a significant decrease in the ZT group compared to the placebo and mebeverine groups (P <0.05). Moreover, the participants in the ZT group reported a significant decrease in fatigue compared to the other two groups (P <0.05). CONCLUSION: This study confirmed the positive effect of ZT on IBS symptoms, especially pain, bloating, constipation, and bowel movements.