Treatment of Irritable Bowel Syndrome (IBS)
Start all IBS patients with regular exercise and first-line dietary advice, then escalate to soluble fiber (ispaghula 3-4 g/day), followed by tricyclic antidepressants (amitriptyline 10 mg daily, titrating to 30-50 mg) for persistent symptoms, reserving psychological therapies for those refractory to 12 months of pharmacological treatment. 1
Establishing the Diagnosis and Patient Education
Make a positive diagnosis based on symptoms alone when alarm features (rectal bleeding, unintentional weight loss, family history of colorectal cancer, iron deficiency anemia) are absent and basic blood and stool tests are normal—colonoscopy is not indicated in typical IBS 1
Explain IBS as a disorder of gut-brain interaction, discussing how diet, stress, and cognitive-behavioral-emotional responses to symptoms affect the gut-brain axis 2
For IBS with diarrhea (IBS-D) patients with atypical features (nocturnal diarrhea, prior cholecystectomy, age ≥50 years, autoimmune disease, severe watery diarrhea, duration <12 months, weight loss), test for bile acid malabsorption before labeling as IBS 1
First-Line Treatments: Lifestyle and Dietary Modifications
Prescribe regular exercise to all patients as it provides significant symptom improvement 1, 2
Provide initial dietary counseling focusing on reducing excessive lactose, fructose, sorbitol, caffeine, and alcohol intake 2
Start soluble fiber (ispaghula/psyllium) at low doses of 3-4 g/day and increase gradually to avoid worsening bloating—this effectively treats global symptoms and abdominal pain 1, 2
Avoid insoluble fiber (wheat bran) as it exacerbates symptoms 1, 2
Consider a low FODMAP diet as second-line dietary therapy only under supervision of a trained dietitian, with systematic reintroduction of foods according to tolerance—do not use this as first-line therapy 1, 2
Do not recommend gluten-free diets unless celiac disease is confirmed 1, 2
Do not recommend IgG antibody-based food elimination diets 1, 2
Trial probiotics for up to 12 weeks and discontinue if no improvement occurs—specific strains cannot be recommended based on current evidence 1, 2
Symptom-Specific Pharmacological Treatments
For Diarrhea-Predominant Symptoms (IBS-D)
Use loperamide 2-4 mg up to four times daily, titrating carefully to reduce stool frequency and urgency while avoiding constipation, abdominal pain, and bloating 1, 2, 3
Consider rifaximin 550 mg three times daily for 14 days as second-line therapy—FDA-approved for IBS-D with proven efficacy for global symptoms, though effects on abdominal pain are limited 2, 3
Prescribe 5-HT3 receptor antagonists (alosetron, ondansetron) as second-line agents for refractory diarrhea 2
Test for bile acid malabsorption in patients with prior cholecystectomy or suggestive features, and treat with cholestyramine if positive 1, 2
For Constipation-Predominant Symptoms (IBS-C)
Increase dietary fiber to 25 g/day or use ispaghula/psyllium supplements 2
Add osmotic laxatives for more severe constipation 2
For Abdominal Pain and Spasms
Prescribe antispasmodics (anticholinergics) for meal-related pain, though dry mouth, visual disturbance, and dizziness are common side effects 1, 2
Use peppermint oil as an alternative antispasmodic option 2
Second-Line Pharmacological Treatments
Initiate tricyclic antidepressants (TCAs) as the most effective second-line treatment for global symptoms and abdominal pain—start amitriptyline 10 mg once daily at bedtime and titrate slowly to 30-50 mg once daily 1, 2
Explain to patients that TCAs are used as gut-brain neuromodulators, not for depression, to improve medication acceptance 1
Counsel patients about TCA side effects (dry mouth, drowsiness, constipation) that occur early, while benefits may take 3-4 weeks to manifest 1, 4
Continue TCAs for at least 6 months if patients report symptomatic response, then reassess 2
Consider selective serotonin reuptake inhibitors (SSRIs) as alternatives when TCAs are not tolerated or in constipation-predominant IBS, though evidence is weaker than for TCAs 1, 2
Review treatment efficacy after 3 months and discontinue if no response occurs 2
Psychological Therapies for Refractory Cases
Refer for IBS-specific cognitive behavioral therapy (CBT) or gut-directed hypnotherapy when symptoms persist despite first-line treatments or remain refractory to pharmacological treatment for 12 months 1, 2
Consider dynamic (interpersonal) psychotherapy for patients who relate symptom exacerbations to stressors, have associated anxiety or depression, or have relatively short symptom duration 2
Use stress management and relaxation techniques particularly for patients with waxing and waning symptoms rather than chronic pain 2
Referral to Gastroenterology
Refer when diagnostic doubt exists, symptoms are severe or refractory to first-line treatments, or the patient specifically requests specialist opinion 1
Recognize that most IBS patients can be managed in primary care without specialty consultation 4
Common Pitfalls and Important Caveats
Avoid extensive diagnostic testing once IBS diagnosis is established—this reinforces illness behavior and increases healthcare costs 2, 4
Do not perform colonoscopy in typical IBS without alarm features or risk factors for microscopic colitis (female sex, age ≥50, autoimmune disease, nocturnal/severe watery diarrhea, recent onset, weight loss, NSAID/PPI use) 1
Recognize frequent comorbidity with anxiety and depression (present in many IBS patients) and address these conditions as they affect symptom perception and healthcare-seeking behavior, not symptom generation 4
Acknowledge that IBS symptoms relapse and remit over time, requiring periodic treatment adjustments rather than indefinite continuous therapy 2
Understand that excessive fiber supplementation often backfires by worsening abdominal cramps and bloating 4
Be aware that many treatments studied in specific IBS subtypes (IBS-D, IBS-C) have limited data in mixed IBS (IBS-M), though TCAs remain the most effective option across all subtypes 2