Treatment for IBS with Diarrhea
Start with loperamide (2-4 mg up to four times daily) for diarrhea control, and if symptoms persist after 4-12 weeks, add a low-dose tricyclic antidepressant (amitriptyline 10 mg at bedtime, titrating to 30-50 mg) for global symptom improvement and abdominal pain relief. 1, 2
First-Line Approach: Lifestyle and Dietary Modifications
Recommend regular physical exercise to all patients with IBS-D as this improves global symptoms and should be the foundation of treatment. 1, 2
Provide first-line dietary advice including adequate hydration and identifying potential trigger foods (lactose, fructose, sorbitol, gas-producing foods, excessive caffeine). 1, 2
Start soluble fiber (ispaghula/psyllium) at 3-4 g/day, building up gradually to avoid bloating, which is effective for both global symptoms and abdominal pain. 1, 2 Critically, avoid insoluble fiber (wheat bran) as it consistently worsens IBS-D symptoms. 1, 2
If simple dietary measures fail after 4-6 weeks, consider a low FODMAP diet as second-line dietary therapy, but this must be supervised by a trained dietitian with planned reintroduction of foods according to tolerance. 1
Do not recommend food elimination diets based on IgG antibodies as they lack evidence and may lead to unnecessary dietary restrictions. 1, 2
Consider a 12-week trial of probiotics for global symptoms and abdominal pain, though no specific strain can be recommended; discontinue if no improvement occurs. 1, 2
First-Line Pharmacological Treatment for Diarrhea Control
Loperamide is the first-line pharmacological agent for reducing stool frequency, urgency, and improving consistency in IBS-D. 1, 2 Start at 2-4 mg up to four times daily, titrating carefully to avoid side effects including abdominal pain, bloating, nausea, and constipation. 1, 2
Antispasmodics with anticholinergic properties (such as dicyclomine) can be effective for abdominal pain and global symptoms, particularly when symptoms are exacerbated by meals. 1, 2 Common side effects include dry mouth, visual disturbance, and dizziness. 1
Peppermint oil is an effective antispasmodic option for abdominal pain with a favorable side effect profile. 3
Second-Line Pharmacological Treatment for Persistent Symptoms
Tricyclic antidepressants (TCAs) are the most effective second-line drug for global symptoms and abdominal pain in IBS-D. 1, 2, 4 Start amitriptyline at 10 mg once daily at bedtime and titrate slowly to a maximum of 30-50 mg once daily. 1, 2 Careful explanation of the rationale for their use as gut-brain neuromodulators is required, emphasizing they are not being prescribed for depression. 1
Continue TCAs for at least 6 months if the patient reports symptomatic response, then reassess. 3
Selective serotonin reuptake inhibitors (SSRIs) may be considered as an alternative second-line neuromodulator for global symptoms when TCAs are not tolerated, though evidence is weaker. 1
Third-Line Treatment Options
Rifaximin (550 mg three times daily for 14 days) is FDA-approved for IBS-D and is effective for improving global symptoms, abdominal pain, and stool consistency. 5, 6, 4 It has the most favorable safety profile among approved agents and can be repeated if symptoms recur. 6, 7
5-HT3 receptor antagonists (such as alosetron) are effective for severe IBS-D, particularly in women, but carry a risk of ischemic colitis and severe constipation, limiting their use. 1, 6, 7
Eluxadoline (a mixed opioid receptor drug) is an efficacious option for IBS-D but has limited international availability. 1, 6, 7
Special Considerations
In patients with prior cholecystectomy or nocturnal diarrhea, consider testing for bile acid malabsorption using SeHCAT scanning or serum 7α-hydroxy-4-cholesten-3-one. 1 If confirmed, cholestyramine (bile acid sequestrant) may be effective. 1
Avoid codeine for diarrhea control as it is more likely to cause sedation and drug dependency compared to loperamide. 1
Psychological Therapies for Refractory Symptoms
- When symptoms persist despite 12 months of pharmacological treatment, consider IBS-specific cognitive behavioral therapy or gut-directed hypnotherapy, both of which are effective for global symptoms and abdominal pain. 1, 3, 2, 4
Critical Pitfalls to Avoid
Never use opioids for chronic abdominal pain management due to risks of dependence and complications. 3
Do not recommend gluten-free diets unless celiac disease has been confirmed. 1, 2
Review treatment effectiveness after 3 months and discontinue if there is no response. 3
Recognize that complete symptom resolution is often not achievable; the goal is symptom relief and improved quality of life. 3