What is the recommended evaluation and management of abdominal pain in a patient with constipation‑predominant irritable bowel syndrome (IBS‑C) without alarm features?

Management of Abdominal Pain in IBS-C Without Alarm Features

For abdominal pain in constipation-predominant IBS without alarm features, start with soluble fiber (psyllium 3–4 g/day) and peppermint oil as first-line therapy, escalate to tricyclic antidepressants (amitriptyline 10 mg nightly, titrated to 30–50 mg) if pain persists after adequate constipation treatment, and reserve linaclotide 290 mcg daily for refractory cases when both pain and constipation remain inadequately controlled. 1

Initial Evaluation: Confirm IBS-C Diagnosis

• Establish a positive diagnosis using Rome criteria: abdominal pain ≥12 weeks in the past 12 months with at least two features—pain relief with defecation, onset associated with change in stool frequency, or onset associated with change in stool form 2

• Perform baseline screening to exclude organic disease: complete blood count, C-reactive protein or ESR, celiac serology (IgA tissue transglutaminase with total IgA), and fecal calprotectin in patients <45 years with any diarrheal component 3

• Rule out alarm features that would mandate colonoscopy: age ≥50 years at symptom onset, unintentional weight loss, rectal bleeding, anemia, nocturnal symptoms that awaken the patient, fever, or family history of inflammatory bowel disease or colorectal cancer 2

First-Line Treatment: Dietary and Lifestyle Interventions

• Initiate soluble fiber (ispaghula/psyllium) at 3–4 g daily and titrate upward gradually to minimize bloating; this improves both global IBS-C symptoms and abdominal pain 1

• Avoid insoluble fiber (wheat bran) because it consistently worsens bloating, abdominal pain, and overall symptom burden in IBS-C 1

• Recommend regular aerobic exercise to all IBS-C patients as foundational therapy, as it independently improves global symptom scores 1

• Provide basic dietary counseling: limit excess caffeine, allow adequate time for regular morning defecation, and correct unnecessary self-imposed dietary restrictions 1

Second-Line Treatment: Antispasmodics for Meal-Related Pain

• Use peppermint oil as the preferred antispasmodic for meal-related abdominal pain before escalating to other agents; it has a favorable side-effect profile compared with anticholinergic drugs 1

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

Third-Line Treatment: Address Constipation Before Escalating Pain Therapy

• Add polyethylene glycol (PEG) osmotic laxative if constipation persists after 4–6 weeks of fiber therapy; titrate the dose to symptom response, with abdominal discomfort being the most common adverse effect 1

• Re-evaluate PEG efficacy after 3 months and discontinue if meaningful improvement is not achieved 1

Fourth-Line Treatment: Tricyclic Antidepressants for Refractory Pain

• Prescribe amitriptyline for persistent abdominal pain after adequate constipation treatment is in place; start at 10 mg nightly and titrate slowly (by 10 mg weekly) to a target of 30–50 mg daily 1

• Ensure concurrent laxative therapy is maintained when prescribing tricyclics to mitigate anticholinergic-induced worsening of constipation 1

• Continue effective tricyclic therapy for at least 6 months before considering discontinuation if sustained symptomatic improvement is reported 1

• Counsel patients about common adverse effects: dry mouth, visual disturbances, and dizziness 1

• Consider SSRIs as an alternative when tricyclics are not tolerated or exacerbate constipation, although supporting evidence is weaker 1

Fifth-Line Treatment: Prescription Secretagogues for Combined Pain and Constipation

• Prescribe linaclotide 290 mcg once daily on an empty stomach (≥30 minutes before the first meal) when both abdominal pain and constipation remain inadequately controlled despite first-line therapies; high-quality trials demonstrate significant benefit for both symptoms 1, 4

• Diarrhea is the most common adverse event with linaclotide, occurring as the mechanism of action; review efficacy after 3 months and discontinue if no response 1, 4

• Plecanatide 3 mg daily is an alternative secretagogue with comparable efficacy for patients who cannot tolerate or afford linaclotide 1

• Lubiprostone 8 mcg twice daily with food is a conditional third-line option for women with IBS-C; nausea occurs in ~19% versus 14% with placebo 1

Sixth-Line Treatment: Psychological Therapies for Refractory Symptoms

• Offer IBS-specific cognitive-behavioral therapy (CBT) or gut-directed hypnotherapy when symptoms remain refractory after at least 12 months of optimal pharmacologic management; both modalities reduce overall symptom burden 1

• Prioritize psychological therapies for patients whose symptoms are stress-related, associated with anxiety or depression, or of relatively short duration 1

Critical Pitfalls to Avoid

• Do NOT prescribe anticholinergic antispasmodics (dicyclomine, hyoscyamine) for IBS-C based solely on the "IBS" diagnosis without considering the constipation subtype—this will worsen the constipation 1

• Do NOT use opioid analgesics for chronic abdominal pain in IBS because of high risk of dependence, opioid-induced bowel dysfunction, and worsening constipation 1

• Do NOT recommend IgG antibody-based food elimination diets or gluten-free diets unless celiac disease is confirmed; current evidence does not support their use in IBS-C and may lead to unnecessary dietary restrictions 1

• Review treatment efficacy after 3 months and discontinue any therapy that does not provide meaningful benefit 1

• Avoid extensive investigations once an IBS-C diagnosis is established, as unnecessary testing can reinforce illness behavior and delay appropriate treatment 1

Patient Education

• Explain that IBS-C is a gut-brain interaction disorder with a benign, relapsing-remitting course (not progressive); this understanding reduces patient anxiety and improves adherence 1

• Emphasize that substantial improvement in symptoms, social functioning, and quality of life is achievable with appropriate management, though complete cure is unlikely 1