What helps with diarrhea in a patient with irritable bowel syndrome (IBS)?

Management of Diarrhea in Irritable Bowel Syndrome (IBS)

Loperamide is the most effective first-line treatment for diarrhea in IBS, though careful dose titration is necessary to avoid side effects such as abdominal pain, bloating, nausea, and constipation. 1

First-Line Treatments

Dietary and Lifestyle Modifications

• Regular exercise should be recommended to all IBS patients as it can improve overall symptoms 1
• First-line dietary advice should include:
  • Increasing soluble fiber (e.g., ispaghula/psyllium) starting at low doses (3-4g/day) and gradually increasing to avoid bloating 1
  • Avoiding insoluble fiber (e.g., wheat bran) which may worsen symptoms 1
• A low FODMAP diet may be considered as second-line dietary therapy, but should be supervised by a trained dietitian with planned reintroduction of foods according to tolerance 1
• Gluten-free diets are not recommended for IBS management 1

Pharmacological Options

• Loperamide (4-12mg daily) effectively reduces stool frequency and urgency in IBS-D patients 1
  • Can be used in divided doses or as a single 4mg dose at night 1
  • Many patients learn to use it prophylactically before situations where diarrhea would be problematic 1
• Certain antispasmodics may help with global symptoms and abdominal pain, though side effects include dry mouth, visual disturbance, and dizziness 1
• Probiotics may be tried for up to 12 weeks, though no specific strain can be recommended 1

Second-Line Treatments

Neuromodulators

• Tricyclic antidepressants (TCAs) are effective second-line treatments for global symptoms and abdominal pain in IBS 1
  • Start at low dose (e.g., amitriptyline 10mg once daily) and titrate slowly to 30-50mg once daily 1
  • Particularly helpful in diarrhea-predominant IBS as they can normalize rapid small bowel transit 1
• Selective serotonin reuptake inhibitors (SSRIs) may be effective for global symptoms but have less evidence than TCAs 1

Specialized Medications

• 5-HT3 receptor antagonists are among the most efficacious drugs for IBS-D 1
  • Ondansetron can be titrated from 4mg once daily to maximum 8mg three times daily 1
  • Constipation is the most common side effect 1
• Rifaximin (non-absorbable antibiotic) is effective for IBS-D at 550mg three times daily for 14 days 1, 2
  • FDA-approved specifically for IBS-D 2, 3
  • Has a favorable safety profile compared to other approved agents 3, 4
• Eluxadoline (mixed opioid receptor drug) is efficacious for IBS-D but contraindicated in patients with prior sphincter of Oddi problems, cholecystectomy, alcohol dependence, pancreatitis, or severe liver impairment 1, 5

Special Considerations

Bile Acid Malabsorption

• Consider bile acid malabsorption in patients with IBS-D who have atypical features such as nocturnal diarrhea or prior cholecystectomy 1
• Diagnostic testing with 23-seleno-25-homotaurocholic acid scanning or serum 7α-hydroxy-4-cholesten-3-one should be considered in these cases 1
• Cholestyramine may be effective in confirmed bile acid malabsorption, though many patients prefer loperamide due to better tolerability 1

When to Refer to Specialist Care

• Referral to gastroenterology is warranted when:
  • There is diagnostic doubt
  • Symptoms are severe or refractory to first-line treatments
  • The patient requests specialist opinion 1
• Colonoscopy is not routinely indicated in IBS unless alarm symptoms/signs are present or there are risk factors for microscopic colitis 1

Treatment Algorithm

1. Start with dietary modifications and lifestyle changes (regular exercise, soluble fiber)
2. Add loperamide for diarrhea control, carefully titrating the dose
3. Consider antispasmodics for pain and probiotics for global symptoms
4. If inadequate response, move to second-line options:
   • TCAs for pain and diarrhea
   • Consider specialized medications (rifaximin, 5-HT3 antagonists, or eluxadoline) based on symptom severity and contraindications