Comparing the Efficacy of Nitazoxanide Versus Rifaximin in Adult Patients With Irritable Bowel Syndrome Without Constipation

Inclusion Criteria: * Patients 18 years of age or older. * Patients suffering from diarrhea-predominant IBS according to Rome III criteria. * Active symptoms for at least 2 weeks * Abdominal Pain Intensity: weekly average of worst daily (in past 24 hours) abdominal pain score of \> 3.0 on a 0-to-10-point scale and Stool Consistency: at least one stool with a consistency of Type 6 or Type 7 Bristol stool score (BSS) on at least 2 days per week * Report no restriction whatsoever on their diet. Exclusion Criteria: * Presence of liver disease, malignancy, severe malabsorption, bedridden, endocrinological disorders, or severe chronic obstructive pulmonary disease. * Patients who have undergone abdominal surgeries except for appendectomy and/or cholecystectomy and/or hysterectomy. * Patients who consumed any medications that may affect bowel function within the last 2 weeks such as antibiotics, probiotics, prebiotics, antispasmodics, antidiarrheals, narcotics, or any other medication that may alter bowel function * Patients on antidepressants or antipsychotics starting within the last six weeks before eligibility check.