What are the recommended medications for treating constipation?

Recommended Medications for Constipation

For treating constipation, osmotic laxatives (polyethylene glycol, lactulose, or magnesium salts) or stimulant laxatives (senna, bisacodyl, sodium picosulfate) are the preferred first-line pharmacological options. 1

First-Line Medications

Osmotic Laxatives

• Polyethylene Glycol (PEG):

  • Dosage: 17g daily dissolved in 4-8 oz of water, juice, or other beverage 2
  • Advantages: Excellent safety profile, particularly in elderly patients 1
  • Onset of action: 2-4 days 2
  • Duration: Most effective when used for 1-2 weeks 2

• Lactulose:

  • Advantages: Effective osmotic laxative
  • Disadvantages: May cause bloating and flatulence

• Magnesium Salts (magnesium hydroxide, magnesium citrate):

  • Caution: Should be used carefully in patients with renal impairment due to risk of hypermagnesemia 1

Stimulant Laxatives

• Senna, Bisacodyl, Sodium Picosulfate:
  • Dosage example: Bisacodyl 10-15 mg, 2-3 times daily 1
  • Goal: One non-forced bowel movement every 1-2 days 1

Special Considerations

Opioid-Induced Constipation (OIC)

1. Preventive approach: All patients receiving opioid analgesics should be prescribed a concomitant laxative unless contraindicated 1
2. First-line: Osmotic or stimulant laxatives 1
3. Second-line (for unresolved OIC): Peripherally acting μ-opioid receptor antagonists
   • Methylnaltrexone: 0.15 mg/kg every other day (maximum once daily) 1
   • Naloxegol: Another option for persistent OIC 1
   • Note: Avoid these in patients with bowel obstruction or postoperative ileus 1

Faecal Impaction

• Management: Digital fragmentation and extraction of stool, followed by maintenance bowel regimen 1
• Suppositories/Enemas: First-line when digital rectal exam identifies full rectum or impaction 1
• After disimpaction: Consider glycerine suppositories or rectal bisacodyl 1

Elderly Patients

• Preferred agent: PEG (17g/day) offers efficacious and tolerable solution with good safety profile 1
• Avoid:
  • Liquid paraffin in bed-bound patients or those with swallowing disorders (risk of aspiration pneumonia) 1
  • Bulk laxatives in non-ambulatory patients with low fluid intake (risk of obstruction) 1

Second-Line Options for Specific Conditions

For Irritable Bowel Syndrome with Constipation

• Linaclotide: Guanylate cyclase-C agonist, highly efficacious but may cause diarrhea 1
• Lubiprostone: Chloride channel activator, less likely to cause diarrhea but nausea is common 1

Important Cautions

1. Bulk-forming laxatives (psyllium):

   • Not recommended for opioid-induced constipation 1
   • Must be taken with adequate fluid (at least 8 oz) to prevent intestinal obstruction 3
   • Inferior to PEG and other options for chronic constipation 4

2. Enemas: Contraindicated in patients with:

   • Neutropenia or thrombocytopenia
   • Paralytic ileus or intestinal obstruction
   • Recent colorectal or gynecological surgery
   • Recent anal or rectal trauma
   • Severe colitis or abdominal infection
   • Toxic megacolon
   • Undiagnosed abdominal pain
   • Recent pelvic radiotherapy 1

Non-Pharmacological Approaches

• Ensure privacy and comfort for defecation
• Proper positioning (small footstool to assist gravity)
• Increased fluid intake
• Increased physical activity within patient limits
• Optimized toileting schedule (attempt defecation 30 minutes after meals) 1

Remember that medication choice should be guided by the underlying cause of constipation, patient comorbidities, and medication interactions. For persistent constipation despite appropriate first-line therapy, referral for specialized testing may be warranted.