Comparison of Rimegepant and Placebo for Pain in IBS

Twenty-four participants with non-constipation IBS and chronic abdominal pain will be recruited for enrollment. Participants will meet specific Rome III IBS diagnostic criteria. Inclusion criteria: * Participants will be 18-70 years of age. * Participants will have non-constipation IBS \[that is IBS-D (diarrhea), IBS-M (mixed), or IBS-U (unspecified)\] with chronic abdominal pain diagnosed in their medical records at Mayo Clinic with chronic pain documented for ≥ 3 months. * Participants will have subjective pain ratings of ≥ 30 on the 100 mm VAS during at least 7 consecutive days of the 2 week run-in period for enrollment. * Participants will be capable of providing informed consent. Exclusion criteria: * Diagnosis of moderate-severe depression as per HADS ≥15; * Alcohol or illicit substance dependence or abuse in the past 12 months; * Dementia, unprovoked seizure history, seizure disorder; * Pregnancy (all women of childbearing potential will be required to have a negative pregnancy test prior to initiation, and will be on a highly effective method of contraception, as detailed in the consent form); * Significant change or increase in antidepressant or pain medications within the last four weeks; significant change in primary treatment interventions for pain in the past four weeks; * Medically unstable * Severe hepatic or renal impairment, such as baseline AST or ALT ≥ 2.5 X upper normal limit or end-stage renal disease with estimated glomerular filtration rate or creatinine clearance \<15mL/min. Although Rimegepant is rarely associated with abnormal circulating liver enzymes, we shall exclude patients with baseline AST or ALT greater than 2.5 times the upper limit of normal. * Concomitant use of strong CYP3A4 inhibitors and strong or moderate CYP3A4 inducers. * Participants who report nausea several times per week or daily on the baseline bowel disease questionnaire (question # 16) will be excluded from the study because of the low risk of nausea induced by the treatment which was estimated at approximately 3% for rimegepant compared to 1% for placebo.