What is the recommended management approach for a patient with irritable bowel syndrome with constipation (IBS‑C)?

Management of IBS-C (Irritable Bowel Syndrome with Constipation)

Start with linaclotide 290 mcg once daily on an empty stomach as first-line pharmacological therapy for IBS-C, as this is the only agent with high-quality evidence demonstrating improvement in both abdominal pain and bowel frequency using FDA-approved composite endpoints. 1, 2

Initial Patient Education and Diagnostic Confirmation

• Establish a positive diagnosis based on Rome IV criteria (abdominal pain at least 1 day per week for 3 months, associated with defecation changes) without extensive testing in patients under 45 years without alarm features (unintentional weight loss, blood in stool, fever, anemia, family history of colon cancer or inflammatory bowel disease). 3, 1

• Explain that IBS-C is a disorder of gut-brain interaction with a benign but relapsing/remitting course—complete cure is unlikely, but substantial improvement in symptoms and quality of life is achievable. 3, 4, 1

• Avoid colonoscopy unless alarm features are present, as extensive testing after diagnosis is established provides no benefit and increases patient anxiety. 3, 4, 1

First-Line Lifestyle and Dietary Interventions (Start Here for All Patients)

• Prescribe regular physical activity as the foundation of treatment, as exercise provides significant benefits for constipation and global symptom management. 3, 4, 1

• Start soluble fiber supplementation (ispaghula/psyllium) at 3-4 g/day and gradually increase to avoid bloating, as this improves global symptoms and abdominal pain. 3, 4, 1

• Avoid insoluble fiber (wheat bran) as it consistently worsens symptoms, particularly bloating. 4, 1

• Establish regular time for defecation and ensure adequate sleep hygiene. 1

First-Line Pharmacological Therapy

Linaclotide 290 mcg once daily is the recommended first-line agent because two large randomized controlled trials demonstrated a combined responder rate of 12-13% versus 3-5% with placebo for the FDA composite endpoint (≥30% improvement in abdominal pain plus increase in complete spontaneous bowel movements). 1, 2

Administration Details for Linaclotide:

• Take on an empty stomach at least 30 minutes before the first meal of the day. 2
• Do not crush or chew the capsule. 2
• Counsel patients about diarrhea as the most common adverse effect, which may lead to discontinuation in a small proportion of patients. 1, 2

Alternative First-Line Agent:

• Lubiprostone is the second-line option when linaclotide is ineffective, not tolerated, or unaffordable, with moderate-quality evidence showing small but measurable improvement in global IBS-C symptoms. 1

• Plecanatide 3 mg once daily is another guanylate cyclase-C agonist option with similar efficacy to linaclotide. 5

Symptom-Specific Pharmacological Management

For Abdominal Pain and Cramping:

• Use antispasmodics with anticholinergic properties (dicyclomine) as first-line therapy for abdominal pain, particularly when symptoms are meal-related. 4, 1

• Peppermint oil may be useful as an alternative antispasmodic, though evidence is more limited. 3, 4, 1

For Bloating:

• Trial probiotics for 12 weeks for global symptoms and bloating—no specific species or strain can be recommended. 4, 1
• Discontinue if no improvement after 12 weeks. 4, 1

Second-Line Neuromodulator Therapy (For Refractory Pain)

Start amitriptyline 10 mg once daily at bedtime and titrate slowly to 30-50 mg once daily for refractory abdominal pain, as tricyclic antidepressants provide modest relief of global symptoms and pain. 4, 1

• Provide clear explanation that TCAs are used as gut-brain neuromodulators for pain modulation, not for depression. 4, 6, 1

• Continue for at least 6 months if the patient reports symptomatic improvement. 4, 1

• Monitor for QT-interval prolongation as a potential adverse effect. 1

• SSRIs are not recommended for IBS-C unless a co-existing mood disorder is present, as pooled data from five randomized trials showed no benefit for global relief or abdominal pain. 1

Dietary Therapy for Refractory Symptoms

Consider a supervised trial of low FODMAP diet delivered in three phases (restriction, reintroduction, personalization) for persistent symptoms refractory to first-line measures, as this approach is particularly effective but requires professional guidance by a trained dietitian to avoid nutritional deficits. 3, 4, 6, 1

• A gluten-free diet is not recommended unless the patient has confirmed celiac disease or non-celiac gluten sensitivity. 4, 1

Psychological Therapies (For Refractory Cases After 12 Months)

Refer for IBS-specific cognitive behavioral therapy or gut-directed hypnotherapy when symptoms persist despite pharmacological treatment for 12 months, as these brain-gut behavior therapies are specifically designed for IBS and differ from psychological therapies that target depression and anxiety alone. 3, 4, 6, 1

Agents NOT Recommended as Primary Therapy for IBS-C

• Osmotic laxatives (polyethylene glycol) and stimulant laxatives (senna) should not be used as primary treatments because evidence supporting their efficacy specifically in IBS-C is very limited, despite proven effectiveness for chronic idiopathic constipation. 1

• Avoid IgG-based food allergy testing as true food allergy is rare in IBS. 4, 6

Treatment Monitoring and Adjustment

• Review treatment efficacy after 3 months and discontinue ineffective medications. 4, 1

• Recognize that symptoms may relapse and remit over time, requiring periodic adjustment of treatment strategy. 4, 1

• Adjust the duration and frequency of visits to accommodate mental health needs and ongoing monitoring. 6

Multidisciplinary Care Coordination

Build collaborative links with gastroenterology dietitians and gastropsychologists to coordinate high-quality care. 3, 6, 1

• Refer to a dietitian if the patient consumes considerable intake of foods that trigger IBS symptoms, shows dietary deficits or nutritional deficiency, shows recent unintended weight loss, or requests dietary modification advice. 3, 1

• Refer to a gastropsychologist if IBS symptoms or their impact are moderate to severe, the patient accepts that symptoms are related to gut-brain dysregulation, and has time to devote to learning new coping strategies. 3, 1

Critical Pitfalls to Avoid

• Do not pursue extensive testing once IBS diagnosis is established in patients under 45 without alarm features. 3, 4, 1

• Avoid opioids for chronic abdominal pain management due to risks of dependence and complications. 6

• Do not use low-dose TCAs to address concurrent psychological symptoms—if a mood disorder is present, use an SSRI instead. 3, 6

• Engage in shared decision-making with patients when choosing therapy, as treatment choices may be influenced by patient preferences, out-of-pocket expenses, and insurance coverage. 3