What are the treatment options for constipation?

Treatment Options for Constipation

Start with osmotic laxatives (polyethylene glycol, lactulose, or magnesium salts) or stimulant laxatives (senna, bisacodyl) as first-line pharmacological therapy, combined with lifestyle modifications including increased fluid intake and physical activity. 1, 2

Initial Assessment

Before initiating treatment, evaluate for reversible causes and severity 1, 2:

• Rule out impaction and bowel obstruction through abdominal and digital rectal examination 1, 2
• Check for metabolic causes: hypercalcemia, hypokalemia, hypothyroidism, diabetes mellitus 1
• Review medications and discontinue non-essential constipating agents 2
• Plain abdominal X-ray can assess fecal loading extent if clinically indicated 1, 2

Non-Pharmacological Management (First-Line for All Patients)

Implement these measures regardless of constipation severity 1, 2:

• Increase fluid intake to adequate levels 1, 2
• Increase physical activity and mobility within patient's capabilities, even bed-to-chair transfers 1, 2
• Optimize toileting: ensure privacy, proper positioning (small footstool helps), attempt defecation 30 minutes after meals 1, 2
• Dietary fiber (25 g/day) may be added if fluid intake is adequate, though evidence for pain reduction is mixed 1, 3
• Abdominal massage can reduce symptoms and improve bowel efficiency, particularly with neurogenic problems 1, 2

Important caveat: Bulk laxatives like psyllium and methylcellulose are not recommended for opioid-induced constipation and have limited effectiveness in cancer-related constipation 1. Water-insoluble fibers work better than soluble fibers for laxation 4.

Pharmacological Treatment Algorithm

Step 1: First-Line Laxatives

Choose between osmotic or stimulant laxatives 1, 2:

Osmotic laxatives (preferred):

• Polyethylene glycol (PEG): 17 g/day 2
• Lactulose: 30-60 mL daily 1
• Magnesium hydroxide: 30-60 mL daily 1
• Magnesium citrate 1

Stimulant laxatives:

• Bisacodyl: 10-15 mg, 2-3 times daily 1
• Senna: 2 tablets every morning, maximum 8-12 tablets per day 1
• Sodium picosulfate 1

Goal: One non-forced bowel movement every 1-2 days 1

Warning: Magnesium salts can cause hypermagnesemia in renal impairment—use cautiously 1, 2

Step 2: If Constipation Persists

• Reassess for obstruction and check for impaction 1
• Add another laxative from a different class if monotherapy fails 1
• Consider prokinetic agent (metoclopramide 10-20 mg PO 3-4 times daily) if gastroparesis suspected 1

Step 3: Rectal Interventions for Impaction

When digital rectal exam identifies full rectum or fecal impaction 1, 2:

• Glycerin suppositories 1
• Bisacodyl suppository once daily 1
• Manual disimpaction (digital fragmentation and extraction) 1, 2
• Enemas (Fleet, saline, or tap water) 1

Contraindications for enemas: neutropenia, thrombocytopenia, paralytic ileus, intestinal obstruction, recent colorectal/gynecological surgery, recent anal/rectal trauma, severe colitis, toxic megacolon, undiagnosed abdominal pain, recent pelvic radiotherapy 1

Opioid-Induced Constipation (Special Considerations)

All patients on opioids require prophylactic laxatives unless pre-existing diarrhea 1, 2:

Standard Approach:

• Start laxatives with opioid initiation: stool softener plus stimulant laxative (senna/docusate, 2 tablets every morning) 1
• Increase laxative dose when increasing opioid dose 1
• Avoid bulk laxatives (psyllium, methylcellulose) for opioid-induced constipation 1

Refractory Opioid-Induced Constipation:

When standard laxatives fail 1, 2:

• Methylnaltrexone 0.15 mg/kg subcutaneously every other day (maximum once daily) 1, 2
• Do not use in postoperative ileus or mechanical bowel obstruction 1
• Alternative peripherally-acting μ-opioid receptor antagonists: naloxegol 1
• Lubiprostone (prostaglandin analog) can be combined with methylnaltrexone 1
• Linaclotide (guanylate cyclase-C agonist) effective for chronic idiopathic constipation 1

The NCCN guidelines specifically recommend methylnaltrexone for constipation unresponsive to standard laxative therapy, as it relieves opioid-induced constipation while preserving analgesia 1.

Special Populations

Elderly Patients:

• Ensure toilet access, especially with decreased mobility 1, 2
• PEG 17 g/day is safe and effective 2
• Avoid liquid paraffin in bedridden patients or those with swallowing disorders (aspiration risk causing lipoid pneumonia) 2
• Monitor for dehydration and electrolyte imbalances when using diuretics or cardiac glycosides concomitantly 2

Cancer Patients:

• Approximately 50% of advanced cancer patients experience constipation 2
• Anticipatory management when prescribing opioids 1
• Individualize laxatives based on cardiac/renal comorbidities and medication interactions 2

Common Pitfalls to Avoid

• Do not rely on fiber alone for opioid-induced or cancer-related constipation—it is ineffective 1
• Do not use enemas in immunocompromised or post-surgical patients 1
• Do not forget to increase laxatives when escalating opioid doses 1
• Do not use methylnaltrexone in bowel obstruction 1
• Monitor magnesium levels in renal impairment patients on magnesium-based laxatives 1, 2