What is the management of opioid-induced bowel syndrome?

Management of Opioid-Induced Bowel Syndrome

For patients with opioid-induced bowel syndrome, treatment should begin with lifestyle modifications and traditional laxatives, progressing to peripherally acting μ-opioid receptor antagonists (PAMORAs) for refractory cases, while ensuring appropriate opioid prescribing practices and minimizing opioid doses when possible. 1

Definition and Pathophysiology

Opioid-induced bowel dysfunction (OIBD) refers to a constellation of gastrointestinal adverse effects associated with opioid therapy, with constipation being the most common and problematic manifestation. The condition affects 40-80% of patients on chronic opioid therapy 1.

Key features of opioid-induced constipation (OIC) include:

• New or worsening symptoms when initiating, changing, or increasing opioid therapy
• At least 2 of the following occurring >25% of the time:
  • Straining during defecation
  • Lumpy or hard stools
  • Sensation of incomplete evacuation
  • Sensation of anorectal obstruction/blockage
  • Manual maneuvers to facilitate defecation
  • Fewer than 3 spontaneous bowel movements per week 1

The pathophysiology involves activation of peripheral μ-opioid receptors in the enteric nervous system, resulting in:

• Decreased peristaltic activity
• Reduced mucosal secretions
• Delayed gastric emptying
• Slowed intestinal transit
• Increased intestinal fluid absorption
• Disordered anal sphincter function 1

Assessment and Diagnosis

When evaluating a patient with suspected OIC:

1. Take a detailed history of:

   • Defecation patterns
   • Dietary habits
   • Stool consistency
   • Symptoms of dyssynergic defecation
   • Alarm symptoms (blood in stool, weight loss)

2. Review medical history for:

   • Comorbid illnesses
   • Regular medication use
   • Other potential causes of constipation

3. Exclude other contributors to constipation:

   • Pelvic outlet dysfunction
   • Mechanical obstruction
   • Metabolic abnormalities
   • Other medications 1

Management Algorithm

Step 1: Optimize Opioid Therapy

• Ensure appropriate indication for opioid therapy
• Use the minimum necessary opioid dose
• Consider opioid rotation to less constipating options (e.g., transdermal fentanyl instead of oral morphine)
• Consider combination opioid agonist/antagonist agents (e.g., oxycodone + naloxone) 1
• For patients with suspected narcotic bowel syndrome, consider gradual supervised opioid withdrawal with pain specialist involvement 1

Step 2: Lifestyle Modifications

• Increase fluid intake
• Engage in regular moderate exercise as tolerated
• Respond promptly to the urge to defecate
• Eat slowly and chew food thoroughly
• Plan smaller, more frequent meals
• Establish a regular toileting schedule 1

Step 3: Traditional Laxatives

• First-line therapy: Osmotic laxatives (e.g., polyethylene glycol)
• Alternative options:
  • Stimulant laxatives (e.g., senna, bisacodyl)
  • Stool softeners
  • Bulk-forming agents
  • Lubricants 1

Step 4: Peripherally Acting μ-Opioid Receptor Antagonists (PAMORAs)

For patients with inadequate response to laxatives:

• Naloxegol: Starting dose 25mg once daily (12.5mg in patients with renal insufficiency)
  • Monitor for abdominal pain and diarrhea
  • Contraindicated in patients with known/suspected GI obstruction or at risk of recurrent obstruction 2
• Methylnaltrexone: Induces laxation in 50-60% of patients with advanced disease and OIBD who don't respond to traditional laxatives 3

Step 5: Nutritional Support (if needed)

• If malnourished, try oral supplements/dietary adjustments
• If oral feeding unsuccessful and patient not vomiting, consider gastric feeding
• If gastric feeding unsuccessful, try jejunal feeding
• If jejunal feeding fails and patient is malnourished, consider parenteral support 1

Special Considerations

Monitoring

• Monitor for adverse effects of PAMORAs:
  • Abdominal pain (21% with naloxegol 25mg)
  • Diarrhea (9% with naloxegol 25mg)
  • Nausea (8% with naloxegol 25mg)
  • Potential opioid withdrawal symptoms (3% with naloxegol 25mg) 2

Cautions

• Patients on methadone have higher frequency of gastrointestinal adverse reactions with PAMORAs 2
• Avoid PAMORAs in patients with:
  • GI obstruction
  • Infiltrative GI tract malignancy
  • Recent GI tract surgery
  • Diverticular disease
  • Ischemic colitis 2

Prevention

• Consider prophylactic laxative therapy when initiating opioid treatment
• Optimize nutritional status before any surgical procedure
• Delay PEG or stoma placement in severely malnourished patients 1

Treatment-Resistant Cases

For patients with persistent symptoms despite standard approaches:

• Consider small intestinal bacterial overgrowth (SIBO) as a potential complication
• Evaluate for SIBO with hydrogen/methane breath testing or small bowel aspirate culture
• If SIBO confirmed, treat with rifaximin 550mg twice daily for 1-2 weeks 4
• Consider prokinetics to improve intestinal motility and prevent SIBO recurrence 4

By following this systematic approach to opioid-induced bowel syndrome, clinicians can effectively manage this common complication of opioid therapy and improve patients' quality of life while maintaining adequate pain control.