What are the treatment options for a patient with severe constipation?

Treatment of Severe Constipation

For severe constipation, immediately perform a digital rectal examination to rule out fecal impaction, then initiate polyethylene glycol (PEG) 17g once or twice daily as first-line therapy, combined with increased fluid intake and physical activity. 1

Immediate Assessment Required

Before starting any treatment, you must:

• Rule out fecal impaction via digital rectal examination—this is critical as impaction requires different management 1, 2
• Exclude bowel obstruction through physical examination and consider plain abdominal X-ray if clinically indicated 2, 1
• Check for metabolic causes: corrected calcium, potassium, thyroid function, and glucose (though complete metabolic panels have low diagnostic utility unless other clinical features warrant them) 1, 2
• Review and discontinue constipating medications when feasible (opioids, anticholinergics, antipsychotics) 1, 3

First-Line Pharmacological Treatment

Start with osmotic laxatives as the foundation:

• Polyethylene glycol (PEG) 17g once or twice daily is the preferred first-line agent with superior safety profile and minimal risk of dependency 1, 4
• Alternative osmotic agents include lactulose 30-60 mL twice to four times daily or milk of magnesia 1 oz twice daily (costs approximately $1 or less per day) 1, 4
• Stimulant laxatives (senna 10-15mg or bisacodyl 10-15mg, 2-3 times daily) are equally appropriate as first-line therapy, particularly for opioid-induced constipation 1

Important caveat: Magnesium-based laxatives should be used cautiously in renal impairment due to hypermagnesemia risk 2, 4

Management of Fecal Impaction

If digital rectal examination identifies fecal impaction:

• Disimpaction is required first (usually through digital fragmentation and extraction of stool) 2
• Use suppositories and enemas as first-line therapy when rectum is full or impacted 2
• Mineral oil or warm water enemas are effective for fecal impaction 5

Contraindications to enemas: neutropenia, thrombocytopenia, paralytic ileus, intestinal obstruction, recent colorectal/gynecological surgery, recent anal/rectal trauma, severe colitis, toxic megacolon, undiagnosed abdominal pain, or recent pelvic radiotherapy 2

Stepwise Escalation for Persistent Symptoms

If constipation persists despite first-line therapy:

• Add a second laxative: rectal bisacodyl once daily, lactulose, magnesium hydroxide, or magnesium citrate 1
• Do NOT add stool softeners (like docusate) to stimulant laxatives—evidence shows no additional benefit 1

If still unresponsive:

• Consider prokinetic agents if gastroparesis is suspected: metoclopramide 10-20 mg, 2-3 times daily 1, 3
• For opioid-induced constipation specifically: methylnaltrexone 0.15 mg/kg subcutaneously every other day (but NOT in postoperative ileus or mechanical obstruction) 3

For refractory cases:

• Newer secretagogues such as linaclotide, lubiprostone, or plecanatide may be appropriate 1, 6

Supportive Non-Pharmacological Measures

These should accompany—not replace—pharmacological therapy:

• Increase fluid intake to at least 2 liters daily 1, 4
• Encourage physical activity within patient limitations (even bed to chair transfers help) 2, 1
• Increase dietary fiber to approximately 30g/day ONLY if adequate fluid intake is maintained—fiber without adequate hydration worsens constipation 2, 1
• Ensure privacy, comfort, and proper positioning (small footstool may help exert pressure more easily) 2
• Educate on optimal toileting: attempt defecation twice daily, 30 minutes after meals, straining no more than 5 minutes 2, 4

Treatment Goals

Aim for one non-forced bowel movement every 1-2 days, not necessarily daily bowel movements 1, 3

Critical Pitfalls to Avoid

• Do not rely on fiber supplements alone for medication-induced constipation—they are ineffective without adequate hydration 1
• Avoid bulk-forming agents (psyllium) for opioid-induced constipation 2
• Do not use stimulant laxatives long-term without osmotic agents, as this increases risk of colonic dependency and rebound constipation 4
• Reassess for impaction or obstruction if constipation persists despite treatment 1

Special Considerations for Opioid-Induced Constipation

All patients receiving opioid analgesics should be prescribed a concomitant laxative prophylactically, unless contraindicated by pre-existing diarrhea 2, 1

• Osmotic or stimulant laxatives are preferred over fiber 2
• Combined opioid/naloxone medications reduce the risk of opioid-induced constipation 2
• Peripherally acting mu-opioid antagonists (PAMORAs) may be valuable for unresolved opioid-induced constipation 2