What are the treatment options for irritable bowel syndrome (IBS)?

Treatment of Irritable Bowel Syndrome

Begin with regular physical exercise and soluble fiber (ispaghula/psyllium) 3-4 g/day gradually increased to 25 g/day for all IBS patients, then add symptom-specific pharmacotherapy based on predominant bowel pattern. 1

Initial Management Framework

• Establish a positive diagnosis using Rome criteria without extensive testing in patients under 45 years without alarm features (unintentional weight loss, rectal bleeding, recent change in bowel function) to avoid unnecessary investigations that undermine patient confidence 1
• Explain IBS as a disorder of gut-brain interaction with a benign but relapsing-remitting course, introducing how diet, stress, and emotional responses affect the gut-brain axis 1
• Implement regular physical exercise as foundational therapy for all IBS patients, as this provides significant benefits for global symptom management 1

First-Line Dietary Interventions

• Provide initial dietary counseling focusing on identifying and reducing excessive intake of lactose, fructose, sorbitol, caffeine, or alcohol 1
• Start soluble fiber (ispaghula/psyllium) at 3-4 g/day, gradually increasing to 25 g/day to avoid bloating 1
• Avoid insoluble fiber (wheat bran) as it consistently worsens symptoms 1
• Consider a supervised low FODMAP diet trial (10+ weeks for restriction and reintroduction phases) delivered by a trained dietitian for patients with persistent symptoms after 4 weeks of standard dietary advice 1
• Trial probiotics for 12 weeks and discontinue if no improvement in global symptoms, bloating, or abdominal pain 1

Pharmacological Treatment by Predominant Symptom Pattern

For Diarrhea-Predominant IBS (IBS-D)

First-line therapy:

• Prescribe loperamide 4-12 mg daily (either regularly or prophylactically) as the most effective first-line treatment to reduce stool frequency, urgency, and fecal soiling 1

Second-line therapy:

• Consider rifaximin as second-line therapy, though its effect on abdominal pain is limited 1
• Trial cholestyramine for patients with prior cholecystectomy or suspected bile acid malabsorption (approximately 10% of IBS-D patients) 1

Third-line therapy for severe refractory IBS-D in women:

• Alosetron (5-HT3 receptor antagonist) 0.5 mg twice daily, increasing to 1 mg twice daily if needed after 4 weeks, is effective for women with severe diarrhea-predominant IBS who have failed conventional therapy 2
• Critical warning: Alosetron carries boxed warnings for ischemic colitis (incidence 0.2% through 3 months) and serious complications of constipation 2
• Discontinue immediately if constipation develops for 4 consecutive days, or if signs of ischemic colitis occur (rectal bleeding, bloody diarrhea, new or worsening abdominal pain) 2

For Constipation-Predominant IBS (IBS-C)

First-line therapy:

• Begin with polyethylene glycol (osmotic laxative), titrating dose according to symptoms, with abdominal pain being the most common side effect 1
• Alternatively, use stimulant laxatives (senna) as first-line therapy 1

Second-line therapy:

• Prescribe linaclotide 290 mcg once daily on an empty stomach as the preferred second-line agent when first-line therapies fail after 4-6 weeks, as it is the most effective option for IBS-C with strong evidence 1, 3
• Lubiprostone 8 mcg twice daily is an alternative if linaclotide is not tolerated 3

Critical pitfall to avoid:

• Never prescribe anticholinergic antispasmodics (dicyclomine, hyoscine) for IBS-C without adequate laxative therapy, as they reduce intestinal motility and worsen constipation 1, 3

For Abdominal Pain (All Subtypes)

First-line therapy:

• Start antispasmodics with anticholinergic properties (dicyclomine 40 mg four times daily, hyoscine) for meal-exacerbated pain, though dry mouth, visual disturbance, and dizziness are common side effects 1, 4
• Trial peppermint oil as an alternative antispasmodic with fewer side effects 1, 4

Second-Line Neuromodulator Therapy for Refractory Symptoms

When first-line therapies fail after 3 months:

• Initiate tricyclic antidepressants (amitriptyline 10 mg once daily at bedtime) for refractory pain and global symptoms, titrating slowly by 10 mg/week to 30-50 mg daily over at least 6 months if effective 1, 4
• Use selective serotonin reuptake inhibitors (SSRIs) as alternatives when TCAs are not tolerated or when concurrent mood disorder is present 1
• In IBS-C, use TCAs cautiously as they may worsen constipation through anticholinergic effects; ensure adequate laxative therapy is in place 3

Psychological Therapies for Refractory Cases

When symptoms persist despite 12 months of pharmacological treatment:

• Refer for IBS-specific cognitive behavioral therapy or gut-directed hypnotherapy 1, 3
• Consider mindfulness-based stress reduction (8-12 sessions) for patients with prominent psychological stress and negative emotion 1

Treatment Monitoring and Adjustment

• Review treatment efficacy after 3 months and discontinue ineffective medications 1, 3
• Continue TCAs for at least 6 months if the patient reports symptomatic improvement 1, 3
• Manage patient expectations by explaining that treatment aims for symptom relief and improved quality of life, not cure, as complete symptom resolution is often not achievable 1

Critical Pitfalls to Avoid

• Avoid opioids for chronic abdominal pain management due to risks of dependence, complications, and potential worsening of constipation 1, 4
• Do not recommend IgG antibody-based food elimination diets as they lack evidence 3
• Do not recommend a gluten-free diet unless celiac disease has been confirmed 3
• Recognize frequent comorbidity with mental health disorders (anxiety, depression) and consider referral to gastropsychology when symptoms are moderate to severe 1