What are the medications for constipation?

Medications for Constipation

The first-line pharmacological treatment for constipation is polyethylene glycol (PEG 3350), which is recommended at a dose of 17g daily dissolved in 4-8 ounces of liquid, with no clear maximum dose and demonstrated durable response over 6 months. 1, 2

Classification of Constipation Medications

Osmotic Laxatives

• Polyethylene glycol (PEG 3350)

  • Initial dose: 17g daily
  • Cost: $10-45 monthly
  • Mechanism: Osmotic laxative
  • Advantages: Durable response over 6 months, no clear maximum dose
  • Side effects: Bloating, abdominal discomfort, cramping 1

• Magnesium oxide

  • Initial dose: 400-500mg daily
  • Cost: <$50 monthly
  • Caution: Use carefully in renal insufficiency
  • Note: Previous studies used 1,000-1,500mg daily 1

• Lactulose

  • Initial dose: 15g daily
  • Cost: <$50 monthly
  • Note: Only osmotic agent studied in pregnancy
  • Side effects: Bloating and flatulence may limit use 1

Stimulant Laxatives

• Bisacodyl and sodium picosulfate

  • Initial dose: Bisacodyl 5mg daily
  • Maximum dose: 10mg orally daily
  • Cost: <$50 monthly
  • Recommended for: Short-term use or rescue therapy
  • Side effects: Cramping, abdominal discomfort
  • Caution: Prolonged use can cause diarrhea and electrolyte imbalance 1

• Senna

  • Initial dose: 8.6-17.2mg daily
  • Cost: <$50 monthly
  • Note: Also present in many laxative teas
  • Maximum: Recommended maximum is 4 tablets twice per day 1

Intestinal Secretagogues

• Lubiprostone

  • Dose: 24μg twice daily
  • Cost: $374 monthly
  • Mechanism: Acts on chloride channel type 2 in the gut
  • Benefits: May help with abdominal pain
  • Side effects: Diarrhea in some patients 1, 3

• Linaclotide

  • Initial dose: 72-145μg daily
  • Maximum dose: 290μg daily
  • Cost: $523 monthly
  • Benefits: May help with abdominal pain
  • Side effects: Diarrhea 1

• Plecanatide

  • Dose: 3mg daily
  • Cost: $526 monthly
  • Side effects: Diarrhea 1

5-HT4 Agonists

• Prucalopride
  • Dose: 1-2mg daily
  • Maximum dose: 2mg daily
  • Cost: $563 monthly
  • Benefits: May help with abdominal pain
  • Side effects: Headaches and diarrhea 1

Treatment Algorithm

Step 1: Start with non-pharmacological interventions

• Increase fluid intake
• Increase dietary fiber (14g/1,000 kcal intake per day)
• Increase physical activity within patient limits
• Ensure privacy and comfort for defecation 2

Step 2: First-line pharmacological treatment

• PEG 3350 (17g daily) - most effective first-line agent 1, 2
• Can be combined with fiber supplements if needed

Step 3: If inadequate response to PEG

• Add or switch to another osmotic laxative (lactulose or magnesium salts)
• Consider adding a stimulant laxative (bisacodyl, sodium picosulfate, or senna) 1

Step 4: For refractory constipation

• Consider prescription medications:
  • Lubiprostone (24μg twice daily)
  • Linaclotide (72-145μg daily)
  • Plecanatide (3mg daily)
  • Prucalopride (1-2mg daily) 1

Special Considerations

Opioid-Induced Constipation

• Prophylactic bowel regimen recommended
• PEG 3350 as first-line treatment
• Add stimulant laxative if PEG alone is insufficient
• Avoid bulk laxatives (psyllium) for opioid-induced constipation
• Consider methylnaltrexone for opioid-induced constipation (0.15 mg/kg subcutaneously every other day) 1, 2

Palliative Care Context

• For patients with months to weeks of life expectancy:

  • Discontinue non-essential constipating medications
  • Rule out impaction and obstruction
  • Add and titrate bisacodyl 10-15mg daily to TID
  • Goal: One non-forced bowel movement every 1-2 days 1

• For patients with weeks to days of life expectancy:

  • Increase dose of laxative ± stool softener (senna ± docusate, 2-3 tablets BID-TID) 1

Clinical Pearls and Pitfalls

• Pitfall: Relying solely on fiber supplementation for all types of constipation

  • Solution: While fiber can be effective for many patients, those with slow transit constipation or defecatory disorders often do not respond well to fiber alone 4

• Pitfall: Not considering underlying causes of constipation

  • Solution: Rule out impaction, obstruction, hypercalcemia, hypokalemia, hypothyroidism, diabetes mellitus, and medication effects 1

• Pitfall: Inadequate dosing of laxatives

  • Solution: Titrate doses based on symptom response and side effects 1

• Pitfall: Not monitoring for electrolyte imbalances with prolonged stimulant laxative use

  • Solution: Use stimulant laxatives for short-term or rescue therapy when possible 1

• Pitfall: Overlooking the need for specialized referral in refractory cases

  • Solution: Consider referral for patients over 45 years with atypical symptoms, short history, or persistent symptoms despite treatment 2