What medications are used to treat Irritable Bowel Syndrome (IBS)?

Medications for Irritable Bowel Syndrome (IBS)

The treatment of IBS should follow a stepwise approach, starting with dietary modifications and first-line medications (laxatives for constipation, antidiarrheals for diarrhea, and antispasmodics for pain), followed by second-line treatments based on predominant symptoms. 1

First-Line Pharmacological Treatments

For IBS with Diarrhea (IBS-D)

• Antidiarrheals:
  • Loperamide: Initial dose of 4 mg followed by 2 mg every 4 hours or after every unformed stool (maximum 16 mg/day) 1
  • Can be used prophylactically before situations where diarrhea would be problematic 1

For IBS with Constipation (IBS-C)

• Laxatives:
  • Osmotic laxatives (polyethylene glycol) 2, 1
  • Stimulant laxatives (senna) 2
  • Evidence for laxatives in IBS-C is limited, but they are reasonable first-line options due to their effectiveness for constipation generally, low cost, and good tolerability 2

For Abdominal Pain (All IBS subtypes)

• Antispasmodics:
  • Dicyclomine and hyoscine are first-line treatments 2, 1
  • Peppermint oil can also be effective for pain and is considered first-line 2, 1

Second-Line Pharmacological Treatments

For IBS-D

• FDA-approved medications:
  • Eluxadoline: Specifically indicated for IBS-D in adults 3
  • Rifaximin: Non-systemic antibiotic approved for IBS-D 4
  • Alosetron: For severe IBS-D that hasn't responded to other treatments 2
• Other options:
  • Codeine 15-30 mg, 1-3 times daily (may cause sedation) 1
  • Octreotide for severe, persistent diarrhea (100-150 μg subcutaneously three times daily) 1

For IBS-C

• Secretagogues:
  • Linaclotide or plecanatide: These drugs soften stools and accelerate gut transit by activating ion channels on the luminal surface of enterocytes 2, 1
  • Linaclotide is preferred based on efficacy 1
  • Lubiprostone is another option 5

For Pain and Psychological Symptoms

• Neuromodulators:
  • Tricyclic antidepressants (TCAs): Amitriptyline 10-50 mg at bedtime for pain with sleep disturbance 2, 1
  • Selective serotonin reuptake inhibitors (SSRIs): For predominant anxiety/depression, though less effective for pain 1
  • Serotonin-norepinephrine reuptake inhibitors (SNRIs): Duloxetine for visceral pain 1
  • Mirtazapine: For refractory nausea and vomiting 1

Treatment Algorithm

1. Start with dietary modifications and lifestyle changes

   • Low FODMAP diet for moderate to severe symptoms 1
   • Mediterranean diet for psychological-predominant symptoms 1
   • Reduce intake of gas-producing foods 1

2. Add soluble fiber and/or peppermint oil

3. If inadequate response:

   • For IBS-C: Add polyethylene glycol
   • For IBS-D: Add loperamide

4. If still inadequate response:

   • For IBS-C: Add a secretagogue (linaclotide preferred)
   • For IBS-D: Consider rifaximin or eluxadoline

5. For persistent symptoms:

   • Add an antispasmodic or gut-brain neuromodulator (TCAs, SSRIs)

6. For severe or refractory symptoms:

   • Consider psychological therapies (cognitive-behavioral therapy, gut-directed hypnotherapy) 1

Important Considerations

• Complete symptom resolution is often not achievable, and this must be made clear to patients to manage expectations 2
• The efficacy of all drugs for IBS treatment is modest, including newer drugs developed specifically for IBS 2
• Use a symptom diary to identify triggers and monitor response to treatment 1
• Review efficacy after 3 months of treatment and discontinue if no response 1

Caveats and Pitfalls

• Avoid using TCAs in patients with constipation as they may worsen this symptom
• SSRIs may exacerbate diarrhea in some patients with IBS-D
• Rifaximin should not be used for systemic bacterial infections due to limited systemic exposure after oral administration 4
• Eluxadoline should be used with caution in patients with a history of pancreatitis or alcohol abuse
• Patients with hepatic impairment may require dose adjustments for rifaximin, as exposure is significantly higher in these patients 4