Treatment of Irritable Bowel Syndrome
Begin with regular physical exercise and soluble fiber (ispaghula/psyllium 3-4 g/day, gradually increased), then escalate to symptom-specific pharmacotherapy (loperamide for diarrhea, polyethylene glycol for constipation, antispasmodics for pain), and reserve tricyclic antidepressants (amitriptyline 10-50 mg daily) for refractory cases. 1, 2, 3
Foundation: Lifestyle and Initial Dietary Management
Prescribe regular physical exercise to all IBS patients as the cornerstone of treatment, as this improves global symptoms with strong evidence 1, 2, 3
Start soluble fiber (ispaghula or psyllium) at 3-4 g/day and build up gradually to 25 g/day to avoid bloating and gas, which is effective for both global symptoms and abdominal pain 1, 2, 3
Completely avoid insoluble fiber (wheat bran) as it consistently worsens symptoms, particularly bloating 1, 2, 3
Provide dietary counseling focusing on regular meal patterns, adequate hydration, and limiting caffeine, alcohol, and gas-producing foods 2
Trial probiotics for 12 weeks and discontinue if no improvement occurs, though no specific strain can be recommended 1, 2, 3
Symptom-Specific Pharmacotherapy
For Diarrhea-Predominant IBS (IBS-D)
Prescribe loperamide 2-4 mg up to four times daily as first-line treatment to reduce stool frequency, urgency, and fecal soiling 1, 2, 3
Titrate loperamide carefully to avoid abdominal pain, bloating, nausea, and constipation as side effects 1, 2
Consider rifaximin as second-line therapy, though recognize its effect on abdominal pain is limited 1, 3
Trial cholestyramine for patients with prior cholecystectomy or suspected bile acid malabsorption (approximately 10% of IBS-D patients) 3
For Constipation-Predominant IBS (IBS-C)
Begin with polyethylene glycol (osmotic laxative) as first-line treatment, titrating dose according to symptoms, with abdominal pain being the most common side effect 1, 3
Prescribe linaclotide (guanylate cyclase-C agonist) 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, 4
Consider lubiprostone (8 mcg twice daily for IBS-C in women ≥18 years) as an alternative secretagogue if linaclotide is not tolerated 1, 5
Use stimulant laxatives (senna, bisacodyl) as additional options, though specific evidence in IBS-C is limited 1, 3
For Abdominal Pain (All Subtypes)
Prescribe antispasmodics with anticholinergic properties (dicyclomine, hyoscine) for meal-exacerbated pain, but warn patients about dry mouth, visual disturbance, and dizziness 1, 2, 3
Trial peppermint oil as an alternative antispasmodic with fewer side effects 1, 3
Recognize that smooth muscle relaxants (cimetropium, pinaverium, octilonium, trimebutine, mebeverine) show 22% improvement over placebo for global symptoms, primarily through effects on abdominal pain (18% over placebo) and distension (14% over placebo), with no effect on bowel alterations 6
Second-Line Neuromodulator Therapy for Refractory Symptoms
Initiate tricyclic antidepressants (amitriptyline 10 mg once daily at bedtime) for refractory pain and global symptoms, titrating slowly to 30-50 mg daily over at least 6 months if effective 1, 2, 3
Provide careful explanation that TCAs are used as gut-brain neuromodulators, not for depression, and counsel about side effects including dry mouth, drowsiness, and constipation 2, 3
Use selective serotonin reuptake inhibitors (SSRIs) as alternatives when TCAs are not tolerated or when TCAs worsen constipation in IBS-C patients 1, 2, 3
Continue TCAs for at least 6 months if the patient reports symptomatic improvement 1, 3
Second-Line Dietary Therapy
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 4-6 weeks of standard dietary advice 2, 3
Never recommend gluten-free diets unless celiac disease has been confirmed, as evidence does not support their use in IBS 1, 2, 3
Never use IgG antibody-based food elimination diets as they lack evidence and may lead to unnecessary dietary restrictions 1, 2, 3
Psychological Therapies for Persistent Symptoms
Refer for IBS-specific cognitive behavioral therapy or gut-directed hypnotherapy when symptoms persist despite 12 months of pharmacological treatment 1, 2, 3
Consider mindfulness-based stress reduction (8-12 sessions) for patients with prominent psychological stress and negative emotion 3
Recognize that psychological treatments are most effective in patients with overt psychiatric disorders and stress-exacerbated symptoms, but have no effect on constipation and constant abdominal pain 6
Treatment Monitoring and Expectations
Review treatment efficacy after 3 months and discontinue ineffective medications 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 2, 3
Establish a positive diagnosis using Rome criteria without extensive testing in patients under 45 years without alarm features 3
Explain IBS as a disorder of gut-brain interaction with a benign but relapsing-remitting course 3
Critical Pitfalls to Avoid
Never start with insoluble fiber as it will worsen symptoms, particularly bloating 2, 3
Avoid opioids for chronic abdominal pain management due to risks of dependence, complications, and potential worsening of constipation 1, 3
Recognize frequent comorbidity with mental health disorders (anxiety, depression) and consider referral to gastropsychology when symptoms are moderate to severe 3
Avoid extensive investigations once IBS is diagnosed based on symptom criteria in the absence of alarm features 3
In IBS-C patients on TCAs, ensure adequate laxative therapy is in place as TCAs may worsen constipation 1