Treatment Options for Irritable Bowel Syndrome
Begin with lifestyle modifications and soluble fiber, then escalate to symptom-specific pharmacological therapy based on the predominant bowel pattern (diarrhea vs. constipation), reserving neuromodulators and psychological therapies for refractory cases.
First-Line Treatment for All IBS Patients
Regular physical exercise should be recommended to every IBS patient as foundational therapy, as it provides significant benefits for symptom management 1, 2, 3.
Start soluble fiber supplementation with ispaghula (psyllium) at 3-4 g/day, gradually increasing the dose to avoid bloating and gas, which is effective for both global symptoms and abdominal pain 1, 2, 4.
Avoid insoluble fiber such as wheat bran, as it consistently worsens IBS symptoms rather than improving them 1, 2.
Provide clear explanation that IBS is a disorder of gut-brain interaction with a benign but relapsing/remitting course to establish realistic expectations 2, 3.
Dietary Interventions
Consider a supervised trial of a low FODMAP diet delivered in three phases (restriction, reintroduction, personalization) under the guidance of a trained dietitian for patients with persistent symptoms after first-line measures 1, 2, 3, 5, 4.
Do not recommend gluten-free diets unless celiac disease has been confirmed, as evidence does not support their use in IBS 1, 4.
Do not recommend IgG antibody-based food elimination diets, as they lack evidence and may lead to unnecessary dietary restrictions 1, 3.
Trial probiotics for 12 weeks for global symptoms and bloating, but discontinue if no improvement occurs, as no specific strain can be universally recommended 1, 2, 4.
Pharmacological Treatment Based on Predominant Symptoms
For Abdominal Pain and Cramping
Antispasmodics with anticholinergic properties (such as dicyclomine 40 mg four times daily) are effective first-line therapy for abdominal pain, particularly when symptoms are meal-related 1, 2, 6.
In controlled trials, 82% of patients treated with dicyclomine 160 mg daily (40 mg four times daily) demonstrated favorable clinical response compared with 55% on placebo 6.
Peppermint oil may be useful as an alternative antispasmodic for abdominal pain, though evidence is more limited 1, 2.
For Diarrhea-Predominant IBS (IBS-D)
Loperamide 2-4 mg up to four times daily is first-line therapy to reduce stool frequency, urgency, and fecal soiling 1, 2, 4.
Rifaximin (a non-absorbable antibiotic) is effective as second-line therapy for IBS-D, though its effect on abdominal pain is limited 1.
5-HT3 receptor antagonists are effective second-line options for diarrhea when loperamide fails 1.
Consider cholestyramine for patients with prior cholecystectomy or suspected bile acid malabsorption, though it is often less well tolerated than loperamide 2, 7.
For Constipation-Predominant IBS (IBS-C)
Start with polyethylene glycol (osmotic laxative), titrating the dose according to symptoms, with abdominal pain being the most common side effect 1.
If first-line therapies fail, linaclotide 290 mcg once daily on an empty stomach is the preferred second-line agent for IBS-C, addressing both abdominal pain and constipation with strong evidence 1.
Lubiprostone 8 mcg twice daily is an alternative secretagogue if linaclotide is not tolerated, though it has higher rates of nausea 1.
Add bisacodyl 10-15 mg daily as a stimulant laxative if osmotic laxatives are insufficient, with the goal of one non-forced bowel movement every 1-2 days 1.
Critical pitfall: Do not prescribe anticholinergic antispasmodics like dicyclomine in IBS-C patients, as they reduce intestinal motility and enhance water reabsorption, which will worsen the constipation 1.
For Mixed IBS (IBS-M)
- Tricyclic antidepressants (TCAs) are the most effective first-line pharmacological treatment for mixed symptoms, starting with amitriptyline 10 mg once daily at bedtime and titrating slowly to 30-50 mg daily 1, 2, 3.
Second-Line Neuromodulators for Refractory Pain
TCAs (amitriptyline 10-50 mg daily) are effective for global symptoms and abdominal pain when first-line therapies fail, particularly if insomnia is prominent 1, 2, 4.
Start TCAs at 10 mg once daily and increase slowly (by 10 mg/week) to maximum 30-50 mg once daily, and continue for at least 6 months if symptomatic response occurs 1, 2.
TCAs may worsen constipation through anticholinergic effects, so use cautiously in IBS-C and ensure adequate laxative therapy is in place 1.
Selective serotonin reuptake inhibitors (SSRIs) may be effective as second-line neuromodulators when TCAs are not tolerated or worsen constipation, and should be used if there is a concurrent mood disorder 1, 2.
Psychological Therapies for Persistent Symptoms
IBS-specific cognitive behavioral therapy and gut-directed hypnotherapy should be considered when symptoms persist despite 12 months of pharmacological treatment 8, 1, 2, 3, 5, 4.
These brain-gut behavior therapies are specifically designed for IBS and differ from psychological therapies that target depression and anxiety alone 2.
Refer to a gastropsychologist if IBS symptoms are moderate to severe, the patient shows motivational deficiencies affecting self-management, or has impaired quality of life 8.
Treatment Monitoring and Duration
Review treatment efficacy after 3 months and discontinue ineffective medications 1, 2.
TCAs should be continued for at least 6 months if the patient reports symptomatic improvement 1, 2.
Recognize that symptoms may relapse and remit over time, requiring periodic adjustment of treatment strategy 2.
Multidisciplinary Care Coordination
Refer to a specialist gastroenterology dietitian if the patient consumes a diet high in IBS-triggering foods, shows dietary deficits or nutritional deficiency, has recent unintended weight loss, or requests dietary modification advice 8, 2.
Build collaborative links with gastroenterology dietitians and gastropsychologists to coordinate high-quality care 2, 3.
Critical Pitfalls to Avoid
Do not pursue extensive testing once IBS diagnosis is established in patients under 45 without alarm features (unintentional weight loss ≥5%, blood in stool, fever, anemia, family history of colon cancer or inflammatory bowel disease) 8, 2, 3.
Avoid using opioids for chronic abdominal pain management in IBS patients due to risks of dependence and complications 1.
Do not continue ineffective therapies indefinitely, such as docusate (Colace), which lacks efficacy for constipation 1.