What is the recommended treatment for Irritable Bowel Syndrome (IBS) with constipation subtype?

Treatment of IBS with Constipation (IBS-C)

Start with soluble fiber (ispaghula/psyllium) at 3-4 g/day, building up gradually, and if symptoms persist after 4-6 weeks, escalate to linaclotide 290 mcg once daily as the most effective second-line agent for IBS-C. 1, 2, 3

First-Line Treatment: Lifestyle and Dietary Interventions

Exercise and Basic Dietary Modifications

• Recommend regular physical exercise to all IBS-C patients as this improves global symptoms and forms the foundation of treatment 2, 3
• Advise regular meal patterns, adequate hydration (at least 8 cups of fluid daily), and limiting caffeine, alcohol, and gas-producing foods 2, 3

Fiber Therapy

• Begin with soluble fiber (ispaghula or psyllium) at 3-4 g/day, increasing gradually to avoid bloating and gas 1, 2, 3
• Avoid insoluble fiber (wheat bran) entirely as it consistently worsens IBS symptoms, particularly bloating 2, 3
• If soluble fiber fails after 4-6 weeks, add polyethylene glycol (osmotic laxative), titrating the dose according to symptoms 2

Probiotics

• Consider a 12-week trial of probiotics for global symptoms and abdominal pain, though no specific strain can be recommended; discontinue if no improvement occurs 2, 3

Antispasmodics for Pain

• Consider antispasmodics with anticholinergic properties (such as dicyclomine) for abdominal pain and global symptoms, but warn patients about dry mouth, visual disturbance, and dizziness 1, 2
• Peppermint oil may be useful as an alternative antispasmodic 2

Second-Line Treatment: Secretagogues for Persistent Constipation

When first-line therapies fail after 4-6 weeks, escalate to prescription secretagogues, with linaclotide as the preferred agent. 1, 2

Linaclotide (Preferred Second-Line Agent)

• Linaclotide 290 mcg once daily is the most efficacious secretagogue available for IBS-C, with strong recommendation and high-quality evidence 1, 2
• Linaclotide significantly improves abdominal pain, bloating, stool frequency, and stool consistency over 26 weeks of treatment 4
• Warn patients that diarrhea is a common side effect (4.5% discontinuation rate) 1, 4

Lubiprostone (Alternative Second-Line Agent)

• Lubiprostone 8 mcg twice daily with food is an effective alternative if linaclotide is not tolerated 1, 2, 5
• This secretagogue is less likely to cause diarrhea than linaclotide 1
• Warn patients that nausea is a frequent side effect; taking with food and water reduces nausea 1, 5
• Dose adjustment required for hepatic impairment: 8 mcg once daily for severe impairment (Child-Pugh Class C) 5
• Contraindicated in patients with known or suspected mechanical gastrointestinal obstruction 5

Other Secretagogues (Where Available)

• Plecanatide is an efficacious alternative, though diarrhea is equally common as with linaclotide 1
• Tenapanor is effective with strong evidence, but diarrhea is a frequent side effect 1
• Tegaserod is effective but unavailable outside the USA 1

Third-Line Treatment: Neuromodulators for Refractory Pain

When abdominal pain persists despite adequate treatment of constipation, add tricyclic antidepressants (TCAs) as gut-brain neuromodulators. 2, 3

Tricyclic Antidepressants

• Start amitriptyline 10 mg once daily at bedtime, titrating slowly to 30-50 mg daily 2, 3
• Explain to patients that TCAs are used as gut-brain neuromodulators, not for depression 3
• Use cautiously in IBS-C as TCAs may worsen constipation; ensure adequate laxative therapy is in place 2
• Continue for at least 6 months if the patient reports symptomatic response 2

Selective Serotonin Reuptake Inhibitors (SSRIs)

• SSRIs are effective alternatives when TCAs are not tolerated or worsen constipation 2, 3
• SSRIs have a lower side effect profile compared to TCAs 2

Fourth-Line Treatment: Psychological Therapies

Consider psychological therapies when symptoms persist despite 12 months of pharmacological treatment. 1, 2, 3

• IBS-specific cognitive behavioral therapy (CBT) is effective for global symptoms with strong recommendation 1, 2, 3
• Gut-directed hypnotherapy is effective for global symptoms with strong recommendation 1, 2, 3
• Referral can be made earlier based on patient preference if accessible locally 1

Dietary Therapy: Low-FODMAP Diet

• If symptoms persist after first-line fiber therapy, consider a low-FODMAP diet as second-line dietary therapy 2, 3
• This must be supervised by a trained dietitian with planned reintroduction of foods according to tolerance 2, 3
• Do not recommend gluten-free diets unless celiac disease has been confirmed 2, 3
• Never use IgG antibody-based food elimination diets as they lack evidence and may lead to unnecessary dietary restrictions 2, 3

Critical Pitfalls to Avoid

• Never start with insoluble fiber (wheat bran) as it will worsen symptoms, particularly bloating 2, 3
• Avoid extensive investigations once IBS is diagnosed based on symptom criteria in the absence of alarm features 2, 3
• Do not promise complete symptom resolution; the goal is symptom relief and improved quality of life 2
• Review efficacy after 3 months of treatment and discontinue if no response 2
• Recognize frequent comorbidity with mental health disorders and consider referral when necessary 2

When to Refer to Gastroenterology

• Refer when there is diagnostic doubt, severe symptoms, or symptoms refractory to first-line treatments after 12 weeks 3
• Consider referral for severe or refractory IBS symptoms with review of diagnosis and consideration of further targeted investigation 1