What is the recommended treatment for Irritable Bowel Syndrome (IBS) when first diagnosed?

Initial Treatment of Irritable Bowel Syndrome

When IBS is first diagnosed, begin immediately with regular exercise and first-line dietary advice, then add soluble fiber (ispaghula 3-4 g/day, titrated gradually), and consider symptom-specific pharmacotherapy with antispasmodics for pain or loperamide for diarrhea if lifestyle measures alone are insufficient. 1

Foundational Lifestyle Interventions (Start These First)

• Advise all patients to engage in regular physical exercise as this improves global IBS symptoms and should form the foundation of treatment 1, 2
• Provide first-line dietary advice to all patients, focusing on regular meal patterns, adequate hydration, and limiting caffeine, alcohol, and gas-producing foods 1, 2
• Avoid insoluble fiber (wheat bran) entirely as it consistently worsens IBS symptoms, particularly bloating 1, 2

First-Line Pharmacological Treatment

For Global Symptoms and Abdominal Pain

• Start soluble fiber supplementation with ispaghula (psyllium) at 3-4 g/day, building up gradually to avoid bloating and gas, as this is effective for both global symptoms and abdominal pain with strong evidence 1, 2
• Consider antispasmodics with anticholinergic properties for abdominal pain and global symptoms, though warn patients about common side effects including dry mouth, visual disturbance, and dizziness 1, 2
• Peppermint oil is an effective first-line antispasmodic option for pain and bloating 2

For IBS with Diarrhea (IBS-D)

• Loperamide 2-4 mg up to four times daily can reduce stool frequency, urgency, and fecal soiling, but titrate carefully to avoid abdominal pain, bloating, nausea, and constipation 1, 2
• Rifaximin 550 mg three times daily for 14 days is FDA-approved for IBS-D and can be repeated up to two times for symptom recurrence 3

For IBS with Constipation (IBS-C)

• Begin with soluble fiber (ispaghula) at 3-4 g/day, increasing gradually 1, 2
• If fiber fails after 4-6 weeks, add polyethylene glycol (osmotic laxative), titrating the dose according to symptoms 2

Probiotics as First-Line Option

• A 12-week trial of probiotics may be effective for global symptoms and abdominal pain, though no specific species or strain can be recommended; discontinue if no improvement occurs 1, 2

Second-Line Dietary Therapy (If First-Line Measures Fail After 4-6 Weeks)

• A low-FODMAP diet is effective for global symptoms and abdominal pain, but must be supervised by a trained dietitian with planned reintroduction of foods according to tolerance 1, 2
• Do not recommend gluten-free diets unless celiac disease has been confirmed, as evidence does not support their use in IBS 1, 2
• Never use IgG antibody-based food elimination diets as they lack evidence and may lead to unnecessary dietary restrictions 1, 2

When to Escalate to Second-Line Pharmacotherapy

If symptoms persist despite 4-6 weeks of first-line treatments, consider:

• Tricyclic antidepressants (TCAs) starting with amitriptyline 10 mg once daily at bedtime, titrated slowly to 30-50 mg daily, are the most effective second-line treatment for global symptoms and abdominal pain 1, 2
• Provide careful explanation that TCAs are used as gut-brain neuromodulators, not for depression, and counsel about side effects including dry mouth, drowsiness, and constipation 1, 2
• SSRIs may be effective alternatives when TCAs are not tolerated, particularly if TCAs worsen constipation in IBS-C patients 1, 2

Critical Pitfalls to Avoid

• Never start with insoluble fiber as it will worsen symptoms, particularly bloating 1, 2
• Do not use opioids for chronic abdominal pain management due to risks of dependence and complications 2
• Avoid extensive investigations once IBS is diagnosed based on symptom criteria in the absence of alarm features 1, 2
• Do not promise complete symptom resolution; the goal is symptom relief and improved quality of life 2

When to Refer to Gastroenterology

• Refer when there is diagnostic doubt, severe symptoms, or symptoms refractory to first-line treatments after 12 weeks 1
• Consider psychological therapies (CBT specific for IBS or gut-directed hypnotherapy) when symptoms persist despite 12 months of pharmacological treatment 1, 2