How should constipation‑predominant irritable bowel syndrome be managed?

Management of Constipation-Predominant Irritable Bowel Syndrome

Begin with soluble fiber (ispaghula/psyllium) at 3–4 g daily, titrated upward gradually, combined with regular aerobic exercise; if symptoms persist after 4–6 weeks, add polyethylene glycol (PEG) and titrate to response; for refractory cases, escalate to linaclotide 290 µg daily on an empty stomach as the preferred prescription agent. 1, 2

First-Line: Lifestyle and Soluble Fiber

• Recommend regular aerobic exercise to all IBS-C patients as the foundation of therapy, as physical activity independently improves global symptom scores and quality of life. 1, 2

• Start soluble fiber (ispaghula or psyllium) at 3–4 g per day and increase gradually to minimize bloating and gas production; this regimen improves both overall symptoms and abdominal pain. 3, 1, 2

• Explicitly avoid insoluble fiber such as wheat bran, as it consistently worsens bloating, abdominal pain, and overall symptom burden in IBS-C patients. 3, 1, 2

• Provide basic dietary counseling: limit excess caffeine, allow adequate time for regular defecation (especially in the morning), and correct inappropriate self-imposed dietary restrictions that patients often adopt out of fear. 3, 1

• 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. 1, 2

Second-Line: Osmotic Laxatives and Low-FODMAP Diet

• If symptoms persist after 4–6 weeks of soluble fiber, add polyethylene glycol (PEG) and titrate the dose according to symptom response; abdominal discomfort is the most common adverse effect. 1, 2

• Reassess efficacy after 3 months of PEG therapy; discontinue if meaningful improvement has not been achieved. 1, 2

• A supervised low-FODMAP diet may be considered as second-line dietary therapy, but only when delivered in three phases (restriction, reintroduction, personalization) by a trained dietitian with expertise in IBS management. 1, 2

Third-Line: Prescription Secretagogues

• Linaclotide 290 µg once daily on an empty stomach (at least 30 minutes before the first meal) is the preferred prescription agent when first-line therapies fail; high-quality evidence demonstrates significant benefit for both constipation and abdominal pain. 1, 2

• Plecanatide 3 mg once daily is an alternative secretagogue with efficacy comparable to linaclotide for patients who cannot tolerate or afford linaclotide. 1, 4, 5, 6

• Lubiprostone 8 µg twice daily with food is a conditional third-line option for women with IBS-C; moderate-certainty evidence shows modest benefit, but nausea occurs in approximately 19% versus 14% with placebo. 1, 2

• Review efficacy after 3 months of secretagogue therapy; discontinue if no response, as diarrhea is the most common adverse event and reflects the mechanism of action. 1, 2

Management of Persistent Abdominal Pain

• For meal-related abdominal pain, use peppermint oil as an antispasmodic before escalating to other agents; it has a favorable side-effect profile compared to anticholinergics. 3, 1, 2

• Explicitly avoid anticholinergic antispasmodics (dicyclomine, hyoscyamine) in IBS-C, as they reduce intestinal motility and enhance water reabsorption, which will worsen the constipation. 1, 2

• Tricyclic antidepressants (amitriptyline) are the most effective option for persistent abdominal pain after adequate constipation treatment; start at 10 mg nightly and titrate slowly (by 10 mg per week) to 30–50 mg daily. 3, 1, 2

• When prescribing TCAs in IBS-C, ensure concurrent laxative therapy is in place to mitigate anticholinergic-induced worsening of constipation. 1, 2

• Continue effective TCAs for at least 6 months before considering discontinuation if the patient reports symptomatic improvement. 3, 1, 2

• Selective serotonin reuptake inhibitors (SSRIs) may be considered as an alternative when TCAs are not tolerated or worsen constipation, although supporting evidence is weaker. 1, 2

Fourth-Line: Psychological Therapies for Refractory Symptoms

• IBS-specific cognitive-behavioral therapy (CBT) and gut-directed hypnotherapy should be offered when symptoms remain refractory after at least 12 months of optimal pharmacologic management; both modalities reduce overall symptom burden. 3, 1, 2

• Psychological therapies are particularly beneficial for patients who relate symptom exacerbations to stressors, have associated anxiety or depression, or have symptoms of relatively short duration. 3, 1, 2

Patient Education and Communication

• Provide a clear explanation that IBS-C is a disorder of gut-brain interaction with a benign, relapsing-remitting course (not progressive); this reduces anxiety about unexplained symptoms and prevents unnecessary referrals or potentially hazardous treatments. 3, 1, 2

• Introduce the concept of the gut-brain axis using simple analogies such as "sensitive gut" or "brain-gut interactions," explaining how anxiety (like before an examination) can cause bowel symptoms. 3

• Address patient fears directly, particularly concerns about cancer, which are extremely common and often unspoken. 3, 2

• Keeping a two-week symptom diary helps identify dietary triggers, stressors, and patterns that exacerbate symptoms and guides treatment choices. 3, 1, 2

Critical Pitfalls to Avoid

• Do not prescribe anticholinergic antispasmodics (dicyclomine, hyoscyamine) in IBS-C based solely on the "IBS" diagnosis without considering the constipation subtype; this is a critical error that will worsen the constipation. 1, 2

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

• Do not recommend gluten-free diets unless celiac disease has been confirmed; current evidence does not support their use in IBS-C. 1, 2

• Do not continue docusate (Colace), as it lacks efficacy for constipation and adds no benefit to other laxative therapy. 1

• Avoid extensive investigations once an IBS-C diagnosis is established 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), as unnecessary testing can reinforce illness behavior. 1, 2

• Recognize the high placebo response (averaging 47% in trials), which may reflect the value of the therapeutic relationship and adequate time for explanation; this wears off in the following months. 3