What is the best stool softener for constipation?

Best Stool Softener for Constipation

Polyethylene glycol (PEG) is the best stool softener for constipation, recommended as a first-line treatment with strong evidence supporting its efficacy and safety. 1

First-Line Treatment Options

Osmotic Laxatives (Preferred)

• Polyethylene glycol (PEG): 17g daily with 8oz water

  • Most effective and safe, particularly in elderly patients 1
  • Works by drawing water into the gut to hydrate stool 2
  • Highest quality evidence supporting its use

• Alternatives to PEG:

  • Lactulose: 15-30ml twice daily 1
  • Magnesium hydroxide (avoid in renal impairment) 1

Stimulant Laxatives

• Bisacodyl: 10-15mg daily
• Senna: 2-3 tablets twice daily
• Work by irritating luminal sensory nerve endings, stimulating colonic motility 2

Important Considerations

Docusate Sodium (Not Recommended)

• Despite widespread use, docusate has limited efficacy:
  • Studies show no significant increase in stool water content 3
  • No effect on stool weight, frequency, or transit time 3
  • Randomized trials found docusate plus sennosides was actually less effective than sennosides alone 4

Bulk-Forming Laxatives

• Psyllium and other bulk laxatives are not recommended for medication-induced constipation 1
• While psyllium showed superior stool softening compared to docusate in one study 5, it's contraindicated for opioid-induced constipation 2

Treatment Algorithm

1. Start with PEG 17g daily with adequate fluid intake
2. If inadequate response after 2-3 days: Add stimulant laxative (bisacodyl 10-15mg or senna)
3. For refractory constipation: Consider adding lactulose 30-60mL 2-4 times daily 1
4. For opioid-induced constipation that doesn't respond to above:
   • Consider peripherally acting μ-opioid receptor antagonists (PAMORAs) such as naldemedine or naloxegol 2, 1
   • Methylnaltrexone 0.15 mg/kg subcutaneously every other day may be used 1

Lifestyle Modifications

• Increase fluid intake
• Increase physical activity within patient limits
• Optimize toileting (attempt defecation twice daily, 30 minutes after meals) 1

Monitoring

• Track bowel movement frequency and consistency weekly
• Red flags requiring immediate attention: severe abdominal pain, no bowel movement for >3 days, vomiting, signs of bowel obstruction 1

Common Pitfalls to Avoid

• Relying solely on stool softeners without stimulant laxatives
• Inadequate prophylactic laxative dosing
• Using bulk-forming laxatives for medication-induced constipation
• Delaying escalation to more effective treatments when first-line fails 1