How to manage opioid-induced constipation?

Management of Opioid-Induced Constipation

For opioid-induced constipation, start with traditional laxatives as first-line treatment, and if these fail, use peripherally acting μ-opioid receptor antagonists (PAMORAs) like naldemedine or naloxegol. 1

Understanding Opioid-Induced Constipation (OIC)

OIC occurs via activation of enteric μ-receptors, resulting in:

• Increased non-propulsive contractions in the intestines
• Increased colonic fluid absorption
• Stool desiccation
• Increased rectal sensory threshold
• Increased anal sphincter tone

These effects lead to harder stool and less frequent, less effective defecation, affecting 40-80% of patients on chronic opioid therapy 1.

First-Line Management

Preventive Approach

• Start a prophylactic bowel regimen when initiating opioid therapy 2
• Implement lifestyle modifications:
  • Increase fluid intake to at least 8 glasses daily
  • Gradually increase dietary fiber to 20-25g per day
  • Increase physical activity within patient limits
  • Optimize toileting habits with regular schedule and proper positioning 2

First-Line Pharmacological Treatment

• Traditional laxatives (strong recommendation, moderate quality evidence) 1:
  • Osmotic laxatives: Polyethylene glycol (PEG) - most effective first choice
  • Stimulant laxatives: Bisacodyl, senna - can be added if PEG alone is insufficient
  • Stool softeners: Docusate - may be used in combination with stimulants
  • Avoid bulk-forming laxatives (psyllium, fiber supplements) as they may worsen symptoms 2

Second-Line Management for Laxative-Refractory OIC

When traditional laxatives fail, PAMORAs are recommended:

1. Naldemedine (strong recommendation, high quality evidence) 1
2. Naloxegol (strong recommendation, moderate quality evidence) 1
3. Methylnaltrexone (conditional recommendation, low quality evidence) 1
   • Recommended dose: 0.15mg/kg subcutaneously every other day 2
   • Contraindicated in patients with risk of GI perforation or mechanical bowel obstruction 2

Monitoring and Assessment

• Use the Bowel Function Index to assess severity and monitor response:

  • Ease of defecation
  • Feeling of incomplete bowel evacuation
  • Personal judgment of constipation
  • Score ≥30 indicates clinically significant constipation requiring escalation 2

• Reassess treatment efficacy within 2-4 weeks of initiating therapy 2

• Goal: One non-forced bowel movement every 1-2 days 2

Additional Considerations

• Consider "opioid switching" to less constipating alternatives (e.g., transdermal fentanyl instead of oral morphine) 1
• Combination opioid agonist/antagonist agents (e.g., oxycodone + naloxone) may reduce constipation risk 1
• For intestinal secretagogues like lubiprostone, the AGA makes no recommendation due to evidence gaps 1, though the FDA has approved it for OIC in adult patients with chronic non-cancer pain 3

Common Pitfalls to Avoid

1. Failing to start prophylactic treatment when initiating opioid therapy
2. Using bulk-forming laxatives (psyllium, fiber supplements) which can worsen OIC 2
3. Continuing ineffective treatments without reassessment 2
4. Using docusate alone without stimulant laxatives (insufficient evidence for benefit) 2
5. Using PAMORAs as first-line treatment before trying traditional laxatives 2
6. Overlooking contraindications for PAMORAs in patients with GI obstruction risk 2

By following this algorithmic approach to OIC management, clinicians can effectively address this common and distressing side effect of opioid therapy while maintaining adequate pain control for patients.