LOTRONEX® in Severe Diarrhea-Predominant Irritable Bowel Syndrome (IBS-D)

Inclusion Criteria: 1. Be a female between 18 and 65 years of age (inclusive) at Visit 1. 2. Sign and date a written informed consent form prior to the initiation of any study-related activities, including discontinuation of any prohibited medications. 3. Be diagnosed with severe, diarrhea-predominant IBS. 4. Have experienced chronic IBS symptoms lasting 6 months or longer. 5. Have not responded adequately to other IBS therapy. 6. Be able to read, understand and sign the informed consent and, if applicable, an Authorization to Use and Disclose Protected Health Information form (consistent with Health Insurance Portability and Accountability Act of 1996 \[HIPAA\] legislation), answer the study questionnaires, communicate with the investigator, and understand and comply with protocol requirements. Exclusion Criteria: 1. Has had a period of 3 consecutive days without a bowel movement in the past 14 days. 2. In the past 14 days, has had evidence of chronic or severe constipation, or has a history of chronic or severe constipation, or a history of sequelae from constipation. 3. Has recurrent bowel obstruction of the small intestine or colon. 4. Has had bloody diarrhea or abdominal pain with rectal bleeding in the past 14 days (except rectal bleeding due to hemorrhoids). 5. Has a known biochemical or anatomical abnormality of the gastrointestinal tract. 6. Has a history of thrombophlebitis or hypercoagulable state. 7. Has a history of atherosclerosis. 8. Has any medical or surgical condition that in the judgment of the investigator makes the patient an inappropriate candidate for Lotronex® therapy (e.g., an unstable cardiovascular, autoimmune, renal, hepatic, pulmonary, endocrine, metabolic, gastrointestinal, hematologic, or neurological condition; recent or ongoing malignancy; evidence of hepatic dysfunction; or renal impairment.) 9. Mental impairment of inability to understand the medication guide and instructions for study participation or refusal to comply with protocol. 10. Current (within 7 days from start of Lotronex® use) use of fluvoxamine. 11. Chronic (≥ 6 months) use of narcotics or opioids. 12. The patient has used an investigational drug or participated in an investigational study within 30 days of Visit 1/ Screening Visit. 13. The patient is hypersensitive or has a known negative response to 5-HT3 antagonists. 14. Had a significant adverse event during previous treatment with Lotronex® or is currently using Lotronex®.