What is the recommended management for a patient with irritable bowel syndrome with diarrhea?

Management of Irritable Bowel Syndrome with Diarrhea (IBS-D)

Start with loperamide 4-12 mg daily for diarrhea control, combined with soluble fiber (ispaghula 3-4 g/day gradually increased), regular exercise, and dietary trigger identification as first-line therapy. 1, 2, 3

Initial Diagnosis and Patient Education

Diagnostic Approach

• Make a positive diagnosis based on abdominal pain with altered bowel habit for ≥6 months 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). 1
• Obtain basic screening: full blood count, C-reactive protein or ESR, celiac serology, and fecal calprotectin (in patients <45 years with diarrhea) to exclude inflammatory bowel disease. 1, 3
• Consider colonoscopy only if alarm symptoms, atypical features suggesting microscopic colitis, or diagnostic doubt exists—not routinely. 1, 3

Patient Communication

• Explain IBS as a "sensitive gut" with brain-gut interactions to reduce anxiety about unexplained symptoms. 1
• Emphasize the benign prognosis and relapsing/remitting course. 4
• Clarify that true food allergy is rare but food intolerance (such as bran) is common. 4, 1

First-Line Treatment Strategy

Lifestyle Modifications

• Prescribe regular physical activity to all IBS-D patients as it provides significant benefits for global symptom management. 1, 2, 3
• Recommend keeping a two-week symptom diary to identify dietary triggers, stressors, and symptom patterns. 1

Dietary Management

• Start soluble fiber (ispaghula/psyllium) at 3-4 g/day and increase gradually to avoid bloating and gas production. 1, 3
• Strictly avoid insoluble fiber (wheat bran) as it consistently exacerbates IBS-D symptoms. 1, 3
• Identify and reduce excessive intake of lactose (>280 ml milk/day), fructose, sorbitol, caffeine, and alcohol as these commonly trigger diarrhea. 4, 1
• Consider a trial of lactose exclusion if intake is substantial (>0.5 pint milk/day). 4
• Reserve low-FODMAP diet as second-line dietary therapy, only under supervision of a trained dietitian with planned reintroduction of foods. 1, 2

Common pitfall: Low-FODMAP diet, while effective, can lead to nutritional deficiencies and should not be used as indefinite first-line therapy without dietitian supervision. 5

First-Line Pharmacological Treatment for Diarrhea

• Prescribe loperamide 4-12 mg daily (either regularly or prophylactically before going out) to effectively reduce stool frequency, urgency, and fecal soiling. 4, 1, 2, 3
• Loperamide has minimal effect on abdominal pain, so additional therapy may be needed. 3
• Codeine 30-60 mg, 1-3 times daily can be tried but CNS effects are often unacceptable. 4, 1

First-Line Pharmacological Treatment for Abdominal Pain

• Use antispasmodic agents with anticholinergic properties (such as dicyclomine) as first-line therapy for abdominal pain, particularly when symptoms are meal-related. 4, 1
• Peppermint oil can be used as an alternative antispasmodic. 1

Probiotics

• Consider a 12-week trial of probiotics for global symptoms and bloating, and discontinue if there is no improvement. 1, 3
• No specific strain can be recommended based on current evidence. 3

Second-Line Treatment for Moderate to Severe or Refractory Symptoms

Tricyclic Antidepressants (TCAs)

• Prescribe TCAs for moderate to severe symptoms or when first-line treatments fail, as they are the most effective pharmacological treatment for global symptoms and abdominal pain in IBS-D. 1, 2, 3
• Start amitriptyline at 10 mg once nightly and titrate slowly (by 10 mg/week) according to response and tolerability, up to 30-50 mg once daily. 1, 3
• TCAs have neuromodulatory and analgesic properties independent of their psychotropic effect and alter GI physiology (visceral sensitivity, motility, and secretion) at lower doses than needed for depression. 1
• Clearly explain to patients that TCAs are being used for gut-brain modulation, not depression, to improve adherence and reduce stigma. 3
• Continue TCAs for at least 6 months if the patient reports symptomatic response. 1
• TCAs may aggravate constipation, making them particularly suitable for IBS-D rather than IBS-C. 4

Important caveat: Avoid combining TCAs with other serotonergic agents without vigilance for serotonin syndrome. 3

Selective Serotonin Reuptake Inhibitors (SSRIs)

• SSRIs may be effective as an alternative when TCAs are not tolerated, though evidence quality is lower than for TCAs. 4, 1, 3

FDA-Approved Agents for IBS-D

Rifaximin

• Rifaximin 550 mg three times daily for 14 days is FDA-approved for IBS-D and has the most favorable safety profile among approved agents. 3, 6
• Rifaximin is a non-systemic antibiotic with minimal absorption, making it suitable for gut-targeted therapy. 6

Ondansetron (5-HT3 Receptor Antagonist)

• Ondansetron is a highly efficacious second-line option, starting at 4 mg once daily and titrating to a maximum of 8 mg three times daily. 3
• 5-HT3 receptor antagonists are among the most efficacious drugs for IBS-D. 2

Eluxadoline

• Eluxadoline (mixed opioid receptor modulator) effectively treats IBS-D with improvement in both abdominal pain and stool consistency, though it has absolute contraindications. 3

Alosetron

• Alosetron is approved only for women with severe IBS-D in whom conventional treatment has failed, due to safety concerns including ischemic colitis. 1

Bile Acid Malabsorption Consideration

• Consider bile acid malabsorption in patients with atypical features such as nocturnal diarrhea or prior cholecystectomy. 1, 2, 3
• Cholestyramine may specifically benefit this small subset of patients, though it is less well tolerated than loperamide. 4, 1

Psychological Therapies for Refractory Cases

When to Refer for Psychological Therapy

• Refer for IBS-specific cognitive behavioral therapy (CBT) or gut-directed hypnotherapy when symptoms persist despite first-line treatments. 1
• Psychological therapies are strongly recommended when symptoms are refractory to drug treatment for 12 months. 1
• CBT, dynamic psychotherapy, hypnosis, and stress management/relaxation are effective in reducing abdominal pain and diarrhea, and also reduce anxiety and other psychological symptoms. 1

Identifying Psychological Factors

• Identify features of psychological disorders: disorders of sleep and mood, previous psychiatric disease, history of current or past physical/sexual abuse, poor social support, adverse social factors (separation, bereavement). 4
• Identify somatization: multiple somatic complaints, frequent visits to doctor. 4

Specific Psychological Interventions

• Hypnotherapy is cost-effective in severe refractory cases, particularly in younger patients without serious psychopathology. 4
• Simple relaxation therapy using audiotapes can be tried initially. 4
• Biofeedback may be useful, especially for disordered defecation. 4

Important caveat: Avoid anxiolytics as they have weak treatment effects, potential for physical dependence, and interaction with other drugs and alcohol. 1

Treatment Monitoring and Referral

When to Refer to Gastroenterology

• Refer when there is diagnostic doubt, severe or refractory symptoms, or patient request. 1, 2, 3
• Review treatment efficacy after 3 months and discontinue ineffective therapies. 3

Understanding the Placebo Effect

• The placebo response in IBS trials averages 47%, approximately three times larger than the additional drug effect (16%), which emphasizes the importance of the therapeutic relationship and patient education. 1
• An empathetic approach is key and can improve quality of life and symptoms, and reduce health-care expenditure. 7