What are the treatment options for constipation in an adult patient?

Treatment Options for Constipation in Adults

Start with polyethylene glycol (PEG) 17g mixed with 8 oz of water twice daily as first-line therapy for adult constipation, as it has the strongest evidence for efficacy, excellent safety profile, and durable response over 6 months. 1

First-Line Treatment Approach

• PEG (polyethylene glycol) is the preferred initial therapy with strong recommendation and moderate-quality evidence for chronic idiopathic constipation 1
• Dosing: One capful (17g) mixed with 8 oz of water, administered 1-2 times daily with adequate fluid intake 2, 1
• Expected mild side effects include abdominal distension, loose stool, flatulence, and nausea 1
• PEG demonstrates sustained effectiveness over 6 months without tachyphylaxis 1

Prophylactic Bowel Regimen (Especially for Opioid Users)

• Administer a stimulant laxative (such as senna) with or without a stool softener prophylactically when starting opioids, as patients do not develop tolerance to opioid-induced constipation 2
• Docusate (stool softener) alone is NOT recommended as it has not shown benefit and is less effective than stimulant laxatives alone 2
• Goal: Achieve one non-forced bowel movement every 1-2 days 2

Second-Line Options When PEG Fails

Add Stimulant Laxatives

• Bisacodyl 10-15 mg daily (tablets or suppositories) for short-term use (≤4 weeks) or as rescue therapy 2, 3, 1
• Senna (sennosides) - stimulates myenteric plexus in colon 2
• Sodium picosulfate - stimulates sensory nerves in proximal colon 2, 1
• These agents increase intestinal motility and may cause abdominal cramping 2

Osmotic Laxatives (Alternative or Additive)

• Lactulose - semi-synthetic disaccharide that produces osmotic diarrhea 2
• Magnesium salts - useful for rapid bowel evacuation but avoid in elderly or those with renal insufficiency due to hypermagnesemia risk 2, 3, 1
• Sorbitol - retains fluid in bowel 2

Fiber Supplementation

• Psyllium is the only fiber supplement with demonstrated effectiveness, but only appropriate for patients with low baseline dietary fiber intake 1
• Avoid bulk-forming agents (psyllium, methylcellulose, bran) in patients with established constipation or low fluid intake, as supplemental medicinal fiber is ineffective and may worsen opioid-induced constipation 2
• Fiber should be slowly increased over several weeks to minimize adverse effects 4

Advanced Pharmacologic Options

For Opioid-Induced Constipation (When Laxatives Fail)

• Peripherally acting mu-opioid receptor antagonists when constipation is clearly opioid-related 2:
  • Methylnaltrexone (subcutaneous) - FDA approved for opioid-induced constipation in adults with advanced illness receiving palliative care 2
  • Naloxegol (oral) - FDA approved for opioid-induced constipation in adults with chronic non-cancer pain 2
  • Naldemedine (oral) - FDA approved for opioid-induced constipation in adults with chronic non-cancer pain 2

For Chronic Idiopathic Constipation (Refractory Cases)

• Lubiprostone 24 mcg twice daily with food - FDA approved for chronic idiopathic constipation in adults; also approved for opioid-induced constipation in non-cancer pain 2, 5
• Linaclotide - FDA approved for idiopathic constipation 2
• Prucalopride (5HT4 receptor agonist) - licensed for chronic constipation when other laxatives fail 2

Prokinetic Agents (Limited Role)

• Erythromycin 900 mg/day - may induce antroduodenal migrating complexes but subject to tachyphylaxis 2
• Azithromycin - may be more effective for small bowel dysmotility than erythromycin 2
• Metoclopramide - enhances gastric antral contractility but chronic use limited by risk of tardive dyskinesia 2

Rectal Interventions

• Enemas (sodium phosphate, saline, or tap water) - dilate bowel, stimulate peristalsis, and lubricate stool 2
• Use sparingly with awareness of possible electrolyte abnormalities 2
• Avoid rectal suppositories or enemas in patients with neutropenia or thrombocytopenia 2
• Limit sodium phosphate products to maximum once daily in patients at risk for renal dysfunction 2

Management of Severe Fecal Impaction

• Manual disimpaction must be performed urgently as first step, followed by aggressive oral laxative therapy 3
• After disimpaction: PEG 17g twice daily (34g total) plus bisacodyl 10-15 mg daily 3
• Reassess within 24-48 hours; if no improvement after 3-4 days, consider hospital admission 3

Critical Contraindications and Warnings

• All laxatives are contraindicated in known or suspected mechanical bowel obstruction 2, 5
• Rule out obstruction before initiating therapy, especially if constipation persists despite treatment 2
• Assess for hypercalcemia and other secondary causes if constipation persists 2

Lifestyle Modifications (Adjunctive Only)

• Increase fluid intake, particularly when using osmotic laxatives 2, 1
• Encourage activity and mobility within patient limits 2
• Ensure privacy, comfort, and proper positioning (small footstool may help) 2
• Lifestyle factors alone have limited influence and should not be sole focus of management 2

Treatment Algorithm Summary

1. Start PEG 17g twice daily (or once daily if mild) 1
2. If no response in 24-48 hours, add bisacodyl as rescue therapy 1
3. If constipation persists, reassess for obstruction and add stimulant laxatives or switch to alternative osmotic agents 2
4. For opioid-induced constipation refractory to laxatives, use peripherally acting mu-opioid receptor antagonists 2
5. For chronic idiopathic constipation refractory to above, consider lubiprostone, linaclotide, or prucalopride 2
6. Maintain long-term prevention with PEG at lower frequency once bowel function normalizes 1