What is the best medication for moderate to severe constipation?

Best Medication for Moderate to Severe Constipation

Polyethylene glycol (PEG) 3350 is the best first-line medication for moderate to severe constipation due to its proven efficacy, safety profile, and durability of response. 1

First-Line Treatment Options

Osmotic Laxatives

• Polyethylene glycol (PEG) 3350

  • Initial dose: 17g daily mixed in water or beverage
  • Mechanism: Osmotic laxative that draws water into the intestinal lumen
  • Cost: $10-$45 monthly
  • Advantages:
    • Durable response shown over 6 months 1
    • No maximum dose limit for titration
    • Safe for long-term use up to 12 months 2
    • Does not cause electrolyte imbalances at standard doses
  • Common side effects: bloating, abdominal discomfort, cramping

• Magnesium Oxide

  • Initial dose: 400-500mg daily
  • Caution in renal insufficiency and pregnancy 1
  • Cost: <$50 monthly

• Lactulose

  • Initial dose: 15g daily
  • Only osmotic agent studied in pregnancy 1
  • FDA-approved for treatment of constipation 3
  • Cost: <$50 monthly
  • Side effects: bloating and flatulence may be limiting

Second-Line Options

Stimulant Laxatives

• Bisacodyl

  • Initial dose: 5mg daily
  • Maximum dose: 10mg orally daily
  • FDA-approved as stimulant laxative 4
  • Cost: <$50 monthly
  • Recommended for short-term use or rescue therapy 1
  • Side effects: cramping, abdominal discomfort
  • Caution: prolonged use can cause electrolyte imbalances

• Senna

  • Initial dose: 8.6-17.2mg daily
  • Cost: <$50 monthly
  • Long-term safety and efficacy unknown 1

Third-Line Options (For Refractory Cases)

Prescription Medications

• Prucalopride

  • Initial dose: 1-2mg daily
  • Mechanism: 5-HT4 agonist
  • Strong recommendation for use when OTC agents fail 1
  • Cost: $563 monthly
  • Side effects: headache, abdominal pain, nausea, diarrhea

• Lubiprostone

  • Dose: 24μg twice daily
  • Cost: $374 monthly
  • May benefit abdominal pain 1

• Linaclotide/Plecanatide

  • Intestinal secretagogues
  • Cost: >$500 monthly
  • Side effect: diarrhea may lead to discontinuation

Treatment Algorithm for Moderate to Severe Constipation

1. Start with PEG 3350 17g daily

   • Efficacy typically seen within 24-48 hours 5
   • Titrate dose as needed based on response
   • Can be used safely for long-term management 2

2. If inadequate response after 1 week:

   • Increase PEG 3350 dose (no clear maximum dose) 1
   • Consider adding a stimulant laxative (bisacodyl 5-10mg) for rescue therapy

3. For persistent constipation:

   • Consider switching to or adding magnesium oxide or lactulose
   • Ensure adequate hydration, especially with fiber supplements

4. For refractory cases:

   • Consider prescription medications like prucalopride (strongly recommended by guidelines) 1

Special Considerations

• Elderly patients:

  • PEG 3350 offers efficacious and tolerable solution with good safety profile 1
  • Avoid liquid paraffin in bed-bound patients (risk of aspiration) 1

• Opioid-induced constipation:

  • Osmotic or stimulant laxatives are generally preferred 1
  • Avoid bulk-forming laxatives like psyllium 1

• Monitoring:

  • Regular assessment of response
  • Monitor for electrolyte imbalances with long-term use of stimulant laxatives
  • For magnesium-containing products, use caution with renal impairment 1

Common Pitfalls to Avoid

1. Inadequate dosing - Many patients require dose titration of PEG 3350 for optimal effect
2. Premature discontinuation - Studies show that constipation often recurs after stopping treatment 6
3. Overreliance on stimulant laxatives - Can lead to dependency and electrolyte imbalances
4. Insufficient hydration - Especially important when using fiber or osmotic laxatives
5. Ignoring underlying causes - Consider medication side effects, metabolic disorders, or structural issues

PEG 3350 has demonstrated both short-term efficacy 7 and long-term safety 2, making it the optimal first choice for moderate to severe constipation with the best balance of efficacy, safety, and tolerability.