What is the approach to managing constipation?

Approach to Constipation

Initial Management: Start with Lifestyle and First-Line Laxatives

Begin with polyethylene glycol (PEG) 17g dissolved in 8 ounces of liquid once daily as your first-line pharmacological treatment, combined with lifestyle modifications including increased fluid intake (≥1.5 liters daily) and regular physical activity. 1, 2

Lifestyle Modifications (Implement First)

• Fluid intake: Ensure at least 1.5 liters of water daily, with increased intake during exercise, hot weather, or illness 2
• Physical activity: Encourage regular exercise and mobility within the patient's limits—even minimal movement from bed to chair stimulates bowel function 2
• Toileting routine: Establish regular attempts at defecation 30 minutes after meals to synergize with the gastrocolic reflex 2
• Positioning: Use a small footstool during defecation to achieve a more natural squatting position that facilitates bowel movements 2
• Privacy and comfort: Ensure adequate toilet access and privacy, particularly for elderly or mobility-impaired patients 3, 2

First-Line Pharmacological Treatment

PEG is the gold standard first-line agent with the strongest evidence base 3, 1:

• Dosing: 17g dissolved in 8 ounces of liquid once daily 1
• Efficacy: Increases complete spontaneous bowel movements by approximately 2.9 per week compared to placebo, with durable response over 6 months 1
• Side effects: Abdominal distension, loose stool, flatulence, and nausea 1
• Advantages: Moderate certainty of evidence, good safety profile, and cost-effective (approximately $1 per day) 3, 1

Fiber Supplementation (Mild Constipation or Adjunct)

• Psyllium has the best evidence among fiber supplements, though still low quality 1
• Dosing: Approximately 15g daily 3
• Important caveat: Fiber supplementation without adequate fluid intake can worsen constipation—this is a common pitfall 2
• Avoid in: Non-ambulatory elderly patients with low fluid intake due to risk of mechanical obstruction 4
• Best for: Patients with mild-to-moderate symptoms and fiber-deficient diets 1

Second-Line Options: When PEG Fails

If PEG is ineffective after an adequate trial (at least 4 weeks), consider these alternatives 1:

Osmotic Laxatives

• Lactulose: 15-30 mL daily as a conditional alternative to PEG 1, 2
• Milk of magnesia: 1 oz twice daily (approximately $1 per day) 3
• Caution: Magnesium-containing laxatives should be used cautiously in elderly patients with renal impairment due to hypermagnesemia risk 4

Stimulant Laxatives

• Senna, bisacodyl, or sodium picosulfate are effective options 1, 2
• Particularly useful for: Opioid-induced constipation 3, 2
• Administration tip: Bisacodyl or glycerol suppositories work best when administered 30 minutes after a meal to synergize with the gastrocolic reflex 3

Third-Line: Prescription Secretagogues and Prokinetics

For patients who fail over-the-counter options, strongly consider prescription agents 1:

Secretagogues (Preferred)

• Linaclotide: FDA-approved for IBS-C and chronic idiopathic constipation in adults; 145 mcg once daily for CIC, 290 mcg for IBS-C 5
• Plecanatide: Another guanylate cyclase-C agonist option 1
• Mechanism: Activate ion channels on enterocytes, moving ions and water into the intestinal lumen, softening stools and accelerating transit 3
• Cost consideration: Approximately $7-9 per day compared to $1 for PEG 3

Prokinetics

• Prucalopride: Strongly recommended for refractory cases (not available in the United States but approved elsewhere) 1

Conditionally Recommended

• Lubiprostone: Conditionally recommended with lower strength of evidence compared to linaclotide and plecanatide 1

Special Populations

Opioid-Induced Constipation

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

• First-line: Stimulant laxatives (senna, bisacodyl) or osmotic laxatives (PEG, lactulose) 2
• Combination therapy: Combined opioid/naloxone medications reduce OIC risk through phase II and III studies 3
• Refractory cases: Peripheral opioid antagonists such as methylnaltrexone or naloxegol for unresolved OIC 3, 1

Elderly Patients

Pay particular attention to medication lists, as polypharmacy is a major contributor to constipation in this population 3, 4:

• First-line: PEG 17g daily remains the preferred agent due to efficacy and safety profile 4
• Avoid: Bulk-forming laxatives in non-ambulatory elderly with low fluid intake 4
• Avoid: Liquid paraffin in bed-bound patients or those with swallowing disorders due to aspiration pneumonia risk 4
• Consider: Rectal measures (suppositories or enemas) for patients with swallowing difficulties or repeated fecal impaction; use isotonic saline enemas rather than sodium phosphate enemas 4
• Individualize: Selection based on cardiac and renal comorbidities, potential drug interactions, and adverse effects 4

When to Perform Diagnostic Testing

After discontinuing constipating medications and performing basic blood tests (corrected calcium, thyroid function if clinically indicated), perform a therapeutic trial with fiber and/or laxatives before ordering anorectal testing 3:

• Anorectal tests: Indicated for patients who do not respond to over-the-counter agents 3, 1
• Colonic transit studies: Consider if slow-transit constipation is suspected after laxative failure 3
• Defecography/anorectal manometry: For suspected defecatory disorders 3
• Plain abdominal X-ray: Limited utility but may help image fecal loading extent and exclude bowel obstruction 3

Management of Defecatory Disorders

Pelvic floor retraining by biofeedback therapy rather than laxatives is the treatment of choice for defecatory disorders 3:

• Efficacy: Improves symptoms in more than 70% of patients with defecatory disorders 3
• Mechanism: Trains patients to relax pelvic floor muscles during straining and restore normal coordination 3
• Success factors: Patient and therapist motivation, frequency and intensity of retraining, involvement of behavioral psychologists and dietitians 3

Management of Fecal Impaction

In the absence of suspected perforation or bleeding, manage fecal impaction with disimpaction followed by maintenance bowel regimen to prevent recurrence 3:

• Distal impaction: Digital fragmentation of stool, followed by enema (water or oil retention) or suppository 3
• After partial disimpaction: Administer PEG orally 3
• Proximal impaction: Lavage with PEG solutions containing electrolytes to soften or wash out stool (if no complete bowel obstruction) 3
• Complications to monitor: Urinary tract obstruction, colonic perforation, dehydration, electrolyte imbalance, renal insufficiency, fecal incontinence, stercoral ulcers, rectal bleeding 3

Common Pitfalls to Avoid

• Docusate monotherapy: Ineffective for prevention or treatment—do not rely on this agent alone 2
• Inadequate trial periods: Ensure at least 4 weeks of treatment before declaring failure and escalating therapy 1, 2
• Fiber without fluids: This combination worsens constipation rather than improving it 2
• Waiting until severe: Implement preventive measures early rather than waiting for severe constipation to develop 2
• Ignoring medication review: Many medications cause constipation; withdrawal of inappropriate or unnecessary medications is essential 3, 4