Quality of Life in Diarrhea-predominant Irritable Bowel Syndrome Taking GABA

Inclusion Criteria: * Age \> 18 years and ≤ 75 * A positive diagnosis of IBS-D according to Rome IV criteria. * Both males and females. * Negative relevant additional screening or consultation whenever appropriate * Colonoscopy if there are alarm symptoms (eg. Rectal bleeding, pseudodiarrhea). If the patients' age is \> or = 50 yrs a colonoscopy within 5 years is mandatory. * Availability to participate in the clinical study, confirmed by the signed informed consent form. * Ability to conform to the study protocol. * Patients' ability to complain study protocol procedures. * Subjects who decide to use single or double contraceptive methods not to conceive during study period. Exclusion Criteria: * Patients with IBS-C, IBS-M and IBS-U according to Rome IV criteria. * Presence of any relevant organic, systemic or metabolic disease (particularly significant history of cardiac, renal, neurological, psychiatric, oncology, endocrinology, metabolic or hepatic disease), or abnormal laboratory values that will be deemed clinically significant. * Ascertained intestinal organic diseases, including celiac disease, food allergies or inflammatory bowel diseases (Crohn's disease, ulcerative colitis, diverticular disease, infectious colitis, ischemic colitis, microscopic colitis). * Previous major abdominal surgery. * Active malignancy of any type, or history of a malignancy (patients with a history of other malignancies that have been surgically removed and who have no evidence of recurr…