What is the recommended management for an adult with irritable bowel syndrome who has no alarm features (no weight loss, bleeding, anemia, fever, or history of inflammatory bowel disease)?

Treatment of Irritable Bowel Syndrome

All patients with IBS should begin with regular exercise and first-line dietary advice (soluble fiber), followed by symptom-directed pharmacotherapy, with psychological therapies reserved for those refractory to 12 months of optimal medical management. 1

Establishing the Diagnosis and Doctor-Patient Relationship

• Make a positive diagnosis based on abdominal pain or discomfort associated with altered bowel habit for at least 6 months, in the absence of alarm features (weight loss, rectal bleeding, anemia, fever, nocturnal diarrhea, family history of IBD or coeliac disease). 1

• Order full blood count, C-reactive protein or ESR, coeliac serology, and faecal calprotectin (in patients <45 years with diarrhea) to exclude inflammatory bowel disease. 1

• Establish an empathetic doctor-patient relationship by explaining IBS as a disorder of gut-brain interaction with a benign, relapsing-remitting course—not progressive—which improves quality of life, reduces healthcare visits, and enhances treatment adherence. 1

• Provide information about the nature of the condition, diagnosis, and symptom management options, as patients desire increased empathy, support, and education from clinicians. 1

First-Line Treatment: Lifestyle and Dietary Modifications

Exercise

• Recommend regular aerobic exercise to all IBS patients as foundational therapy, as it improves global symptoms. 1, 2

Dietary Counseling

• Provide first-line dietary advice to all patients, including limiting excess caffeine, allowing adequate time for regular defecation, and correcting inappropriate self-imposed dietary restrictions. 1, 2

• Start soluble fiber (ispaghula/psyllium) at 3–4 g/day and titrate upward gradually to minimize bloating and gas, as it is effective for global symptoms and abdominal pain. 1, 2

• Avoid insoluble fiber (wheat bran) as it consistently worsens symptoms, particularly bloating. 1, 2

• Do NOT recommend IgG antibody-based food elimination diets, as they lack evidence and may lead to unnecessary dietary restrictions. 1, 2

• Do NOT recommend gluten-free diets unless coeliac disease is confirmed. 1, 2

Probiotics

• Consider a 12-week trial of probiotics for global symptoms and abdominal pain; discontinue if no improvement occurs, though no specific strain can be recommended. 1, 2

Low FODMAP Diet (Second-Line Dietary Therapy)

• If symptoms persist after 4–6 weeks of soluble fiber, consider a low FODMAP diet supervised by a trained dietitian with planned reintroduction of foods according to tolerance. 1, 2

Symptom-Directed Pharmacotherapy

For Diarrhea-Predominant IBS (IBS-D)

• Loperamide 2–4 mg up to four times daily (regular or prophylactic dosing) reduces stool frequency, urgency, and fecal soiling; titrate carefully to avoid constipation, bloating, or abdominal pain. 1, 2

• Rifaximin is effective as a second-line agent for global IBS-D symptoms, though its effect on abdominal pain is limited. 1, 2

• 5-HT3 receptor antagonists (e.g., alosetron) are effective as second-line drugs, but alosetron carries serious safety concerns including ischemic colitis and should be avoided. 1, 2

• In patients with nocturnal diarrhea or prior cholecystectomy, consider testing for bile acid malabsorption with SeHCAT scanning or serum 7α-hydroxy-4-cholesten-3-one. 1

For Constipation-Predominant IBS (IBS-C)

• After soluble fiber failure, add polyethylene glycol (PEG) osmotic laxative and titrate to symptom response; abdominal pain is the most common side effect. 2

• Linaclotide 290 mcg once daily on an empty stomach (at least 30 minutes before the first meal) is the preferred second-line agent when first-line therapies fail, with high-quality evidence for both constipation and abdominal pain. 2, 3

• Plecanatide 3 mg daily is an alternative secretagogue with comparable efficacy to linaclotide. 2, 4

• Lubiprostone 8 mcg twice daily with food is a conditional third-line option for women with IBS-C, though it has a higher rate of nausea (19% vs 14% with placebo). 1, 2

• Do NOT prescribe anticholinergic antispasmodics (dicyclomine, hyoscyamine) in IBS-C, as they reduce intestinal motility and worsen constipation. 2

For Abdominal Pain (All Subtypes)

• Certain antispasmodics with anticholinergic properties (e.g., dicyclomine) taken before meals are effective for meal-related abdominal pain and global symptoms, though dry mouth, visual disturbances, and dizziness are common. 1, 2

• Peppermint oil provides an alternative antispasmodic effect with a more favorable side-effect profile. 1, 2

Second-Line Treatment: Neuromodulators for Refractory Symptoms

• Tricyclic antidepressants (amitriptyline) are the most effective second-line treatment for global symptoms and abdominal pain across all IBS subtypes; start at 10 mg nightly and titrate slowly (by 10 mg/week) to 30–50 mg daily. 1, 2

• Continue TCAs for at least 6 months if the patient reports symptomatic response. 1, 2

• In IBS-C, ensure adequate laxative therapy is in place when prescribing TCAs, as they may worsen constipation through anticholinergic effects. 2

• Selective serotonin reuptake inhibitors (SSRIs) may be effective as second-line neuromodulators for global symptoms when TCAs are not tolerated, though supporting evidence is weaker. 1, 2

• The AGA makes a conditional recommendation AGAINST the use of SSRIs for IBS-D specifically. 1

Third-Line Treatment: Psychological Therapies for Persistent Symptoms

• IBS-specific cognitive-behavioral therapy (CBT) and gut-directed hypnotherapy should be offered when symptoms persist despite 12 months of optimal pharmacological treatment, as both reduce overall symptom burden. 1, 2

• CBT is particularly beneficial for patients who relate symptom exacerbations to stressors or have associated anxiety or depression. 2

• Hypnotherapy is especially effective in younger patients without severe psychopathology. 2

Treatment Monitoring and Reassessment

• Review treatment efficacy after 3 months and discontinue any therapy that lacks meaningful benefit. 1, 2

• When TCAs are effective, maintain them for a minimum of 6 months before contemplating discontinuation. 1, 2

Referral to Gastroenterology

• Refer to gastroenterology when there is diagnostic doubt, presence of alarm features, symptoms that are severe or refractory to first-line treatments after 12 weeks, or when the patient requests a specialist opinion. 1

• There is no role for colonoscopy in IBS except in those with alarm symptoms or signs, or those with IBS-D who have atypical features and risk factors for microscopic colitis (female sex, age ≥50 years, coexistent autoimmune disease, nocturnal or severe watery diarrhea, duration <12 months, weight loss, or use of NSAIDs/PPIs). 1

Critical Pitfalls to Avoid

• Do NOT prescribe opioid analgesics for IBS-related pain due to high risk of dependence and opioid-induced bowel dysfunction. 2

• Do NOT continue docusate (Colace) as it lacks efficacy for constipation. 2

• Do NOT prescribe anticholinergic antispasmodics in IBS-C, as they will worsen constipation. 2

• Do NOT perform extensive investigations once IBS is diagnosed, as unnecessary testing reinforces illness behavior. 2

• In patients with functional bowel symptoms in remission or mildly active IBD, consider dietary advice as for IBS (e.g., low FODMAP diet). 1

• Be aware that NSAIDs, PPIs, and SSRIs are potential precipitants of microscopic colitis and should be discontinued in patients with refractory symptoms. 5