What is the recommended treatment for irritable bowel syndrome, including subtype‑specific management?

Treatment of Irritable Bowel Syndrome

Begin with a positive diagnosis using Rome IV criteria, provide patient education about the gut-brain interaction, and initiate lifestyle modifications with soluble fiber and exercise for all patients, then escalate to subtype-specific pharmacological therapy based on predominant symptoms. 1, 2

Initial Management for All IBS Patients

Patient Education and Reassurance

• Explain that IBS is a disorder of gut-brain interaction with a benign, relapsing-remitting course (not progressive) to establish realistic expectations and reduce anxiety. 2, 3
• Address the patient's specific concerns directly rather than ordering extensive investigations once the diagnosis is established based on Rome IV criteria and absence of alarm features (new onset after age 50, rectal bleeding not from hemorrhoids/fissures, unintentional weight loss, iron deficiency anemia, nocturnal diarrhea, family history of colon cancer/IBD/celiac disease). 1, 3
• Introduce the concept of the gut-brain axis and how diet, stress, and cognitive/behavioral/emotional responses affect symptoms. 2

First-Line Lifestyle Modifications

• Prescribe regular physical exercise to all IBS patients as the foundation of treatment. 2, 3
• Provide dietary counseling: balanced diet, adequate time for regular defecation, good sleep hygiene, and limiting excess caffeine. 2, 3

First-Line Dietary Therapy

• Initiate soluble fiber (ispaghula/psyllium) at 3-4 g/day, building up gradually to avoid bloating, which improves global symptoms and abdominal pain across all IBS subtypes. 1, 2, 3
• Avoid insoluble fiber (wheat bran) as it consistently worsens symptoms, particularly bloating, across all IBS subtypes. 1, 2, 3
• Consider a 12-week trial of probiotics for global symptoms and abdominal pain; discontinue if no improvement occurs (no specific strain can be recommended). 2, 3

Subtype-Specific Pharmacological Management

IBS with Diarrhea (IBS-D)

First-Line Pharmacological Therapy

• Loperamide 2-4 mg up to four times daily (regular or prophylactic dosing before outings) is first-line to reduce stool frequency, urgency, and fecal soiling. 1, 2, 4, 3
• Titrate the dose carefully to avoid constipation, bloating, abdominal pain, and nausea. 1, 2, 4, 3
• Loperamide improves stool consistency (32% improvement) and reduces stool frequency (36% improvement) but does not affect overall symptom burden or abdominal pain. 4

Dietary Modifications for IBS-D

• Identify and eliminate dietary triggers including excess lactose (trial exclusion if consuming >280 mL milk/day), fructose, sorbitol, caffeine, and alcohol. 1, 2, 4

Second-Line Therapy for IBS-D

• Rifaximin 550 mg three times daily for 14 days is effective for global IBS-D symptoms, though its effect on abdominal pain is limited. 1, 2, 5
• Consider cholestyramine for patients with cholecystectomy or suspected bile acid malabsorption (approximately 10% of IBS-D patients), though it is often less well tolerated than loperamide. 1, 4

IBS with Constipation (IBS-C)

First-Line Pharmacological Therapy

• After soluble fiber failure at 4-6 weeks, initiate polyethylene glycol (PEG) osmotic laxative, titrating the dose according to symptoms; abdominal pain is the most common side effect. 1, 2, 3

Second-Line Therapy for IBS-C

• Linaclotide 290 mcg once daily on an empty stomach (at least 30 minutes before the first meal) is the preferred second-line agent for IBS-C when first-line therapies fail, addressing both abdominal pain and constipation. 1, 2
• Diarrhea is the most common adverse event with linaclotide, occurring as the mechanism of action. 1, 2
• Lubiprostone 8 mcg twice daily with food is an alternative FDA-approved secretagogue for women with IBS-C, though nausea is the most common side effect (19% vs 14% placebo). 1, 6
• Plecanatide is another alternative secretagogue with similar efficacy to linaclotide. 1

Critical Pitfall for IBS-C

• Do not prescribe anticholinergic antispasmodics (dicyclomine, hyoscyamine) in IBS-C, as they reduce intestinal motility and enhance water reabsorption, which will worsen the constipation. 1, 2

Management of Abdominal Pain (All IBS Subtypes)

First-Line Antispasmodic Therapy

• Anticholinergic antispasmodics (dicyclomine) taken before meals are effective first-line therapy for meal-related abdominal pain and global symptoms; common side effects include dry mouth, visual disturbances, and dizziness. 1, 2, 3
• Peppermint oil provides an alternative antispasmodic effect with a more favorable side-effect profile. 1, 2, 3

Second-Line Neuromodulator Therapy

• Tricyclic antidepressants (amitriptyline) are the most effective drugs for treating IBS across all subtypes, particularly for refractory abdominal pain and global symptoms. 1, 2, 4, 3
• Start amitriptyline at 10 mg once daily at bedtime, titrate slowly (by 10 mg/week) to 30-50 mg daily based on response and tolerability. 1, 2, 4, 3
• Provide careful explanation that TCAs are used as gut-brain neuromodulators, not for depression. 2, 3
• Continue for at least 6 months if the patient reports symptomatic response. 1, 2
• Use TCAs cautiously in IBS-C and ensure adequate laxative therapy is in place, as they may worsen constipation through anticholinergic effects. 1, 2

Alternative Neuromodulator

• Selective serotonin reuptake inhibitors (SSRIs) may be effective as second-line neuromodulators for global symptoms when TCAs are not tolerated or worsen constipation in IBS-C, though evidence is weaker (pooled data from five RCTs show no significant improvement in global relief or abdominal pain). 1, 2

Psychological Therapies for Refractory Symptoms

• IBS-specific cognitive-behavioral therapy (CBT) and gut-directed hypnotherapy should be offered when symptoms persist despite 12 months of pharmacological treatment. 1, 2, 3
• Consider earlier referral for patients who relate symptom exacerbations to stressors or have associated anxiety/depression. 1, 2, 3
• CBT is particularly effective for younger patients without severe psychopathology. 1, 2
• Dynamic (interpersonal) psychotherapy is beneficial for patients who relate symptom exacerbations to stressors, have associated anxiety or depression, or have symptoms of relatively short duration. 1, 2
• Relaxation and stress-management techniques may benefit patients whose symptoms are stress-related and waxing/waning rather than chronic pain. 1, 2

Treatment Monitoring and Follow-Up

• Review treatment efficacy after 3 months and discontinue therapies lacking efficacy. 1, 2, 3
• When TCAs are effective, maintain for a minimum of 6 months before contemplating discontinuation. 1, 2

Critical Pitfalls to Avoid

• Never use opioids for chronic abdominal pain management in IBS due to dependency risk, lack of efficacy, and risk of complications. 2, 4, 3
• 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 a gluten-free diet unless celiac disease has been confirmed by serologic testing. 1, 2
• Avoid extensive investigations once IBS is diagnosed based on Rome IV criteria in patients under 45 without alarm features. 1, 3
• Do not continue ineffective therapies indefinitely; reassess at 3 months. 1, 2, 3

Referral to Gastroenterology

• Refer for diagnostic uncertainty, presence of alarm features, severe or refractory symptoms after 12 weeks of treatment, or when a supervised low-FODMAP diet is needed. 2
• Build collaborative links with gastroenterology dietitians and gastropsychologists to coordinate care. 3