ACG / AGA · 2021

Irritable Bowel Syndrome — Management Guideline

Source: ACG Clinical Guideline: Management of Irritable Bowel Syndrome — American Journal of Gastroenterology, 2021; supplemented by AGA Clinical Practice Guidelines on the Pharmacological Management of Irritable Bowel Syndrome with Constipation and with Diarrhea

Guideline: Strong Guideline: Conditional Guideline: Not recommended ClinicoQ pathway suggestion (not from the cited guideline)

Diagnosis

Diagnostic criteria Diagnosed using Rome IV criteria: recurrent abdominal pain at least 1 day/week in the last 3 months, associated with 2 or more of: related to defecation, change in stool frequency, or change in stool form. Symptom onset at least 6 months before diagnosis.

⚠ Alarm features (investigate before diagnosing)

GI bleeding or unexplained iron deficiency anemia
Unintentional weight loss
Palpable abdominal mass or lymphadenopathy on exam
Family history of colon cancer without age-appropriate screening
Onset of symptoms at age 50 or older without age-appropriate colon cancer screening
Sudden or acute onset of a new change in bowel habit

Initial workup

Test	When to order
Serologic testing for celiac disease (tTG-IgA)	Guideline recommendation: patients with IBS and diarrhea symptoms.
Fecal calprotectin (or lactoferrin) and CRP	Guideline recommendation: suspected IBS with diarrhea symptoms and no alarm features, to help rule out IBD.
Colonoscopy	Guideline recommends AGAINST routine colonoscopy under age 45 without alarm features. Age-appropriate colorectal cancer screening (generally from 45) still applies on its own merits, and a recent negative screening colonoscopy does not need to be repeated for IBS symptoms alone.

✕ Tests the guideline advises against

Routine stool testing for enteric pathogens: Guideline recommends against this in all patients with IBS (not a useful routine test).

CBC / routine general blood panel as an IBS-specific test: Not a specific ACG recommendation for IBS; ordering it is a general clinical judgment call, not a guideline-mandated test — include only if otherwise clinically indicated.

Treatment

General (all subtypes)

1 Low-FODMAP diet trial Strong (Guideline recommendation)

Dose: Full elimination phase, then structured reintroduction of food groups one at a time
Duration: 4-6 week elimination trial
Evidence level: Moderate
Avoid if: Active or high risk of eating disorder; significant unintentional weight loss already present
If no response ClinicoQ pathway: Proceed directly to subtype-specific pharmacologic therapy below

2 Gut-directed psychotherapy (CBT or gut-directed hypnotherapy) Conditional (Guideline recommendation) — for overall IBS symptoms, as part of a comprehensive management strategy rather than a last resort

Dose: -
Duration: Structured multi-session course (typically weekly)
Evidence level: Moderate
Avoid if: Patient declines, or no access to a trained provider
If no response ClinicoQ pathway: Combine with pharmacologic therapy rather than replace it

3 Tricyclic antidepressant (e.g., amitriptyline, desipramine, nortriptyline) Recommended (ACG 2021 guideline recommendation) — for overall IBS symptoms including abdominal pain; AGA 2022 subtype guidelines separately issued a conditional, low-certainty recommendation for the same use

Dose: Start low (10-25 mg at bedtime) and titrate gradually; may increase up to 100 mg at bedtime if needed and tolerated
Duration: Ongoing, reassess after adequate titration
Evidence level: Moderate (ACG 2021); AGA 2022 subtype guidelines rate this Low certainty
Avoid if: Cardiac conduction abnormalities, narrow-angle glaucoma, significant anticholinergic sensitivity (more common side effects in elderly patients)
If no response ClinicoQ pathway: Consider gut-directed psychotherapy in combination, or reassess for subtype-specific pharmacologic therapy

4 Peppermint oil (enteric-coated capsule) Conditional (Guideline recommendation) — for relief of global IBS symptoms

Dose: Guideline does not specify an exact dose; commonly used at 0.2-0.4 mL (or ~90 mg enteric-coated capsule) two to three times daily before meals
Duration: Ongoing, reassess response
Evidence level: Low
Avoid if: May cause heartburn in some patients (enteric coating reduces this risk)
If no response ClinicoQ pathway: Continue alongside other first-line measures; not a replacement for subtype-specific therapy

5 Antispasmodic (AGA 2022 guideline) Conditional (AGA 2022 guideline recommendation, low certainty) — this update supersedes ACG 2021's position of no formal recommendation either way, which was based on the US-available evidence being too old/low-quality at that time

Dose: Agent- and product-dependent; per product labeling (e.g., hyoscine, dicyclomine, otilonium — availability varies by country)
Duration: As needed or scheduled, per agent
Evidence level: Low
Avoid if: Per individual agent labeling
If no response ClinicoQ pathway: Reassess for subtype-specific pharmacologic therapy

IBS-C (constipation-predominant)

1 Fiber supplementation (psyllium) Conditional (Guideline recommendation)

Dose: Start at a low dose and titrate up gradually
Duration: Ongoing, reassess at 4 weeks
Evidence level: Low-Moderate
Avoid if: Severe bloating (may worsen this symptom)
If no response ClinicoQ pathway: Add osmotic laxative or move to a secretagogue below

2 Linaclotide Strong (Guideline recommendation, FDA-approved dose) — reaffirmed as a strong, high-certainty recommendation by AGA 2022

Dose: 290 mcg once daily on an empty stomach
Duration: Reassess response at 4 weeks
Evidence level: High
Avoid if: Known or suspected mechanical GI obstruction; not for patients under 6 years old
If no response ClinicoQ pathway: Try plecanatide or tenapanor, or reassess the diagnosis

3 Plecanatide Strong (Guideline recommendation, FDA-approved dose)

Dose: 3 mg once daily
Duration: Reassess response at 4 weeks
Evidence level: High (AGA 2022: Moderate certainty)
Avoid if: Known or suspected mechanical GI obstruction; not for patients under 6 years old
If no response ClinicoQ pathway: Consider tenapanor or lubiprostone, or refer for specialist GI evaluation

4 Tenapanor (AGA 2022 guideline) Conditional (AGA 2022 guideline recommendation, moderate certainty) — not present in the ACG 2021 guideline; added here from the more recent AGA subtype-specific guideline

Dose: 50 mg twice daily
Duration: Reassess response after 4 weeks; benefit shown for up to 26 weeks
Evidence level: Moderate
Avoid if: Pediatric patients under 6 years old (contraindicated); known/suspected mechanical GI obstruction
If no response ClinicoQ pathway: Consider lubiprostone, or refer for specialist GI evaluation

5 Lubiprostone Conditional (Guideline recommendation)

Dose: 8 mcg twice daily (this is the IBS-C-specific FDA-approved dose — different from the 24 mcg twice daily dose approved for chronic constipation)
Duration: Reassess response at 4 weeks
Evidence level: Low (AGA 2022: Moderate certainty)
Avoid if: Mechanical GI obstruction; use with caution in pregnancy; FDA-approved for women only
If no response ClinicoQ pathway: Refer for specialist GI evaluation

IBS-D (diarrhea-predominant)

1 Rifaximin Recommended (Guideline recommendation, FDA-approved dose)

Dose: 550 mg three times daily
Duration: 14 days
Evidence level: High (AGA 2022: Moderate certainty)
Avoid if: Known hypersensitivity to rifamycin antibiotics
If no response: FDA labeling allows retreatment with the same 14-day course up to twice if symptoms recur after initial response

2 Eluxadoline Conditional (Guideline recommendation)

Dose: 100 mg twice daily with food; reduce to 75 mg twice daily only for mild-to-moderate hepatic impairment or concurrent use of OATP1B1 inhibitors
Duration: Ongoing, reassess periodically
Evidence level: Moderate
Avoid if: Contraindicated (do not use at all): no gallbladder, biliary duct obstruction or sphincter of Oddi dysfunction, history of pancreatitis, alcoholism/alcohol use disorder (>3 drinks/day), severe hepatic impairment, known hypersensitivity to eluxadoline
If no response ClinicoQ pathway: Consider alosetron for severe cases in women

3 Alosetron Conditional (Guideline recommendation) — restricted to women with severe IBS-D who failed conventional therapy

Dose: 0.5 mg twice daily; may increase to 1 mg twice daily if tolerated after a 4-week trial
Duration: Reassess response at 4 weeks
Evidence level: Moderate
Avoid if: History of constipation, bowel obstruction, ischemic colitis, hepatic impairment
If no response ClinicoQ pathway: Refer to a GI specialist

4 Loperamide Not first-line (Guideline notes it does not address abdominal pain, the core IBS-D symptom)

Dose: As needed for diarrhea symptoms only
Duration: -
Evidence level: Low (AGA 2022: Very low certainty)
Avoid if: -
If no response ClinicoQ pathway: -

✕ Treatments the guideline advises against

Bile acid sequestrants (e.g., cholestyramine, colestipol) for IBS-D: Guideline recommends against use for global IBS-D symptoms — bile acid malabsorption is not commonly tested for, making this treatment unreliable in practice.

Probiotics: Guideline recommends against use for global IBS symptoms — evidence is inconsistent across the many available strains and study designs.

Fecal microbiota transplant: Guideline recommends against use — evidence of efficacy is limited and of very low quality.

SSRIs (AGA 2022 guideline): AGA suggests against using SSRIs for primary treatment of global IBS symptoms (low certainty); not addressed by the ACG 2021 guideline. May still be reasonable in patients with coexistent anxiety or depression.

⚠️ Currency note: the diagnostic framework and general management approach are based on the ACG Clinical Guideline: Management of Irritable Bowel Syndrome (American Journal of Gastroenterology, 2021) — the most recent comprehensive ACG guideline on IBS management as of September 2026; ACG has not published a newer edition since. Select pharmacologic details (tenapanor, updated evidence-certainty ratings, and the position on antispasmodics and SSRIs) are supplemented from the more recent AGA Clinical Practice Guidelines on the Pharmacological Management of IBS with Constipation and with Diarrhea (Gastroenterology, 2022). This is an educational summary of current international clinical practice guidelines and does not replace individualized clinical judgment. Final treatment decisions remain the responsibility of the treating physician.