What are the treatment options for Irritable Bowel Syndrome (IBS) with diarrhea?

Treatment of IBS with Diarrhea

Start with loperamide 4-12 mg daily for diarrhea control, combined with soluble fiber (ispaghula 3-4 g/day, gradually increased) and lifestyle modifications as first-line therapy. 1

First-Line Approach

Dietary and Lifestyle Modifications

• Begin with soluble fiber supplementation using ispaghula or psyllium at 3-4 g/day, increasing gradually to avoid bloating and gas production 1
• Avoid insoluble fiber (wheat bran) as it consistently worsens symptoms in IBS-D 1
• Identify and reduce excessive intake of lactose, fructose, sorbitol, caffeine, and alcohol as these commonly trigger diarrhea 1
• Recommend regular physical exercise to all IBS-D patients 2
• Consider a low-FODMAP diet as second-line dietary therapy only under supervision of a trained dietitian with planned reintroduction of foods 1

First-Line Pharmacological Treatment

• Loperamide 4-12 mg daily is the most effective first-line agent for reducing stool frequency, urgency, and fecal soiling 1, 2
• Loperamide has limited effect on abdominal pain, so additional agents may be needed for pain control 3
• Codeine 30-60 mg, 1-3 times daily, can be tried but CNS effects are often unacceptable 1
• Cholestyramine may benefit patients with prior cholecystectomy or suspected bile acid malabsorption, though it is less well tolerated than loperamide 1

Treatment for Abdominal Pain

• Antispasmodic agents, particularly anticholinergics like dicyclomine, are effective for abdominal pain and global symptoms, especially when symptoms worsen after meals 1
• Peppermint oil can be used as an alternative antispasmodic with fewer anticholinergic side effects 1, 3
• Common side effects of anticholinergics include dry mouth, visual disturbance, and dizziness 2

Second-Line Pharmacological Treatments

Neuromodulators

• Tricyclic antidepressants (TCAs) are the most effective second-line treatment for global symptoms and abdominal pain in IBS-D 1
• Start amitriptyline at 10 mg once nightly and titrate slowly (by 10 mg/week) according to response and tolerability, up to 30-50 mg once daily 1
• Continue TCAs for at least 6 months if the patient reports symptomatic response 1
• SSRIs may be effective as an alternative when TCAs are not tolerated, though evidence quality is lower 1, 3
• When prescribing antidepressants, clearly explain they are being used for gut-brain modulation, not depression 3

FDA-Approved Prescription Medications for IBS-D

Rifaximin:

• Rifaximin is a non-absorbable antibiotic effective for IBS-D, though its effect on abdominal pain is limited 2, 4
• The FDA-approved dose is 550 mg three times daily for 14 days 4
• Patients who experience symptom recurrence can be retreated up to two times with the same dosage regimen 4
• Rifaximin can be taken with or without food 4

5-HT3 Receptor Antagonists:

• Alosetron is FDA-approved for IBS-D but has limited international availability 5, 6
• Ondansetron (off-label) can be started at 4 mg once daily and titrated to maximum 8 mg three times daily 2

Eluxadoline:

• Eluxadoline is a μ-opioid and κ-opioid receptor agonist and δ-opioid receptor antagonist effective for IBS-D 3, 5
• Eluxadoline is contraindicated in patients with prior sphincter of Oddi problems, cholecystectomy, alcohol dependence, pancreatitis, or severe liver impairment 3

Psychological Therapies

• Refer for IBS-specific cognitive behavioral therapy (CBT) or gut-directed hypnotherapy when symptoms persist despite first-line treatments 1
• Psychological therapies are strongly recommended when symptoms are refractory to drug treatment for 12 months 1
• These interventions are particularly beneficial for patients who relate symptom exacerbations to stressors or have associated anxiety or depression 2

Probiotics

• Consider a 12-week trial of probiotics for global symptoms and abdominal pain, though no specific strain can be recommended 2
• Discontinue if no improvement occurs after 12 weeks 2

Patient Education and Communication

• Explain the diagnosis clearly and introduce the concept of the gut-brain axis 1
• Reassure that true food allergy is rare but food intolerance is common 1
• Identify psychological factors such as disorders of sleep and mood, history of abuse, poor social support, or somatization 1

Critical Pitfalls to Avoid

• Do not recommend IgG-based food elimination diets as they lack evidence 1
• Do not recommend gluten-free diet unless celiac disease is confirmed 1
• Consider bile acid malabsorption in patients with atypical features such as nocturnal diarrhea or prior cholecystectomy 1
• Refer to gastroenterology when there is diagnostic doubt, severe or refractory symptoms, or patient request 1
• Review treatment efficacy after 3 months and discontinue if no response 2