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

Treatment of Irritable Bowel Syndrome

Begin with lifestyle modifications and dietary interventions, then escalate to symptom-specific pharmacotherapy based on the predominant bowel pattern (diarrhea, constipation, or pain), reserving neuromodulators and psychological therapies for refractory cases.

Initial Management: Patient Education and Lifestyle Foundation

• Establish the diagnosis using Rome criteria without extensive testing in patients under 45 years without alarm features (rectal bleeding, unintentional weight loss, family history of colon cancer, iron deficiency anemia), avoiding unnecessary investigations that undermine patient confidence 1

• Explain IBS as a disorder of gut-brain interaction with a benign but relapsing-remitting course, emphasizing that stress and emotional responses affect the gut-brain axis and that symptoms wax and wane over time 2, 1

• Implement regular physical exercise for all IBS patients as foundational therapy, as this provides significant benefits for global symptom management 3, 1

• Address the patient's specific concerns and beliefs about their condition; consider having patients keep a symptom diary to identify triggers and patterns 2, 1

First-Line Dietary Interventions

• Provide initial dietary counseling focusing on identifying and reducing excessive intake of lactose, fructose, sorbitol, caffeine, or alcohol, as these commonly exacerbate symptoms 2, 1

• Start soluble fiber (ispaghula/psyllium) at 3-4 g/day, gradually increasing to 25 g/day to avoid bloating and gas, while avoiding insoluble fiber (wheat bran) which consistently worsens symptoms 3, 1

• For patients with persistent symptoms after 4 weeks of standard dietary advice, consider a supervised low FODMAP diet trial (10+ weeks for restriction and reintroduction phases) delivered by a trained dietitian 1

• Trial probiotics for 12 weeks and discontinue if no improvement in global symptoms, bloating, or abdominal pain; no specific strain can be recommended based on current evidence 3, 1

• Do not recommend IgG antibody-based food elimination diets or gluten-free diets unless celiac disease has been confirmed, as evidence does not support their use in IBS 3

Pharmacological Treatment by Predominant Symptom Pattern

For Diarrhea-Predominant IBS (IBS-D)

• Prescribe loperamide 4-12 mg daily (either regularly or prophylactically before going out) as the most effective first-line treatment to reduce stool frequency, urgency, and fecal soiling 2, 3, 1

• Consider rifaximin as second-line therapy for global symptoms, though its effect on abdominal pain is limited 3

• Trial cholestyramine for patients with prior cholecystectomy or suspected bile acid malabsorption (approximately 10% of IBS-D patients) 3, 1

• Consider 5-HT3 receptor antagonists as second-line agents when loperamide fails 3

For Constipation-Predominant IBS (IBS-C)

• Begin with polyethylene glycol (osmotic laxative), titrating dose according to symptoms, with abdominal pain being the most common side effect 3, 1

• If osmotic laxatives fail after 4-6 weeks, add bisacodyl (stimulant laxative) 10-15 mg once daily, with a goal of one non-forced bowel movement every 1-2 days 3

• For refractory IBS-C, prescribe linaclotide 290 mcg once daily on an empty stomach (at least 30 minutes before the first meal) as the preferred second-line agent, as it is the most effective FDA-approved secretagogue addressing both abdominal pain and constipation 3, 4

• If linaclotide is not tolerated or not covered by insurance, lubiprostone 8 mcg twice daily with food is an alternative FDA-approved secretagogue for women with IBS-C, though nausea is a common side effect 3, 5

• Critical pitfall: Do not prescribe anticholinergic antispasmodics (dicyclomine, hyoscyamine) in IBS-C, as they reduce intestinal motility and enhance water reabsorption, which will worsen the constipation 3

For Abdominal Pain (All Subtypes)

• Start antispasmodics with anticholinergic properties (dicyclomine 10-20 mg up to four times daily) for meal-exacerbated pain, though dry mouth, visual disturbance, and dizziness are common side effects 2, 3, 1

• Trial peppermint oil as an alternative antispasmodic with fewer side effects 2, 3, 1

• Avoid anticholinergic antispasmodics in IBS-C patients as they will exacerbate constipation 3

Second-Line Neuromodulator Therapy for Refractory Pain

• 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 2, 3, 1

• Explain to patients that TCAs are being used for their pain-modulating effects on the gut-brain axis, not for depression, to improve acceptance 2, 1

• Use TCAs cautiously in IBS-C and ensure adequate laxative therapy is in place, as TCAs may worsen constipation through anticholinergic effects 3

• Use selective serotonin reuptake inhibitors (SSRIs) as alternatives when TCAs are not tolerated or when concurrent mood disorder is present 2, 3, 1

• Review treatment efficacy after 3 months and discontinue if no response; continue TCAs for at least 6 months if the patient reports symptomatic improvement 3, 1

Psychological Therapies for Refractory Cases

• Refer for IBS-specific cognitive behavioral therapy or gut-directed hypnotherapy when symptoms persist despite 12 months of pharmacological treatment 2, 3, 1

• Consider dynamic (interpersonal) psychotherapy for patients who relate symptom exacerbations to stressors, have associated anxiety or depression, or have symptoms of relatively short duration 3

• Recognize frequent comorbidity with mental health disorders (anxiety, depression, history of physical/sexual abuse) and consider referral to gastropsychology when symptoms are moderate to severe 2, 1

Critical Pitfalls to Avoid

• Do not use opioids (codeine, tramadol) for chronic abdominal pain management due to risks of dependence, complications, and potential worsening of constipation 2, 3

• Discontinue docusate (stool softener) immediately as it lacks efficacy for constipation and provides no additional benefit 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 3, 1

• Identify somatization (multiple somatic complaints, frequent doctor visits) and poor social support factors (separation, bereavement) that may require psychiatric referral 2