Treatment Options for Irritable Bowel Syndrome with Diarrhea (IBS-D)
The most effective approach to treating IBS-D follows a stepwise algorithm starting with lifestyle and dietary modifications, followed by antidiarrheals, and progressing to second-line pharmacological therapies based on symptom severity and response. 1, 2
First-Line Treatments
Lifestyle Modifications
- Regular exercise should be recommended to all IBS-D patients as it can improve symptoms 1, 2, 3
- Stress reduction techniques may help manage symptoms by addressing gut-brain axis dysfunction 1
Dietary Interventions
- Soluble fiber (e.g., ispaghula) is effective for global symptoms and abdominal pain, starting at low doses (3-4g/day) and gradually increasing to avoid bloating 1, 2, 3
- Low FODMAP diet can be considered as second-line dietary therapy but should be supervised by a trained dietitian with systematic reintroduction of FODMAPs according to tolerance 1, 2, 3
- Avoid insoluble fiber (e.g., wheat bran) as it may worsen IBS-D symptoms 1, 3
- Probiotics as a group may improve global symptoms and abdominal pain, though no specific strain can be recommended; a 12-week trial is reasonable 1, 3
First-Line Medications
- Loperamide is recommended as an effective first-line treatment for diarrhea in IBS-D, with careful dose titration necessary to minimize side effects such as abdominal pain, bloating, nausea, and constipation 1, 2, 3
- Antispasmodics may help with global symptoms and abdominal pain, though side effects include dry mouth, visual disturbance, and dizziness 3
Second-Line Treatments
Tricyclic Antidepressants (TCAs)
- TCAs are strongly recommended as effective second-line therapy for global symptoms and abdominal pain 1, 2, 3
- Start at low doses (e.g., 10 mg amitriptyline once daily) and titrate slowly to 30-50 mg once daily 1, 3
Selective Serotonin Reuptake Inhibitors (SSRIs)
- SSRIs may be effective for global symptoms, particularly when comorbid anxiety or depression is present 2, 3
FDA-Approved Medications for IBS-D
Rifaximin
- FDA-approved for treatment of IBS-D in adults 4
- Recommended dose is one 550 mg tablet taken orally three times a day for 14 days 4
- Patients who experience symptom recurrence can be retreated up to two times with the same dosage regimen 4
- Effective for global symptoms and stool consistency, though effect on abdominal pain may be limited 1, 5
- Has a favorable safety profile compared to other approved agents 6
Eluxadoline
- FDA-approved for treatment of IBS-D in adults 7
- Mixed opioid receptor drug that is efficacious for IBS-D 3, 8
- Contraindicated in patients with prior sphincter of Oddi problems, cholecystectomy, alcohol dependence, pancreatitis, or severe liver impairment 1, 2, 3
- Side effects include constipation, nausea, and headache 1
5-HT3 Receptor Antagonists
- Considered among the most efficacious treatments for IBS-D 1, 3
- Alosetron is effective but restricted to women with severe IBS-D under a risk management program due to risk of ischemic colitis 3, 6
- Ondansetron (4 mg once daily, titrated to maximum 8 mg three times daily) is a reasonable alternative where alosetron is unavailable 1, 3
- Constipation is the most common side effect 2
Additional Considerations
For Refractory Symptoms
- Consider testing for bile acid malabsorption in patients with refractory IBS-D symptoms 1
- Bile acid sequestrants (e.g., cholestyramine) may be considered for patients with cholecystectomy or suspected bile acid malabsorption 3, 8
- Psychological therapies (cognitive behavioral therapy, hypnotherapy) can be effective for global symptoms and abdominal pain in patients with refractory symptoms 2, 3
Common Pitfalls and Caveats
- Monitor for constipation with 5-HT3 antagonists and eluxadoline 1, 2
- Be aware of the risk of ischemic colitis with alosetron 1, 3
- Recognize that IBS often has psychological comorbidities that may need to be addressed for optimal symptom control 1, 9
- When using rifaximin, be aware that it should not be used for diarrhea complicated by fever or blood in the stool 4