What are the recommended medications for managing constipation?

Medications for Constipation

For chronic idiopathic constipation, start with polyethylene glycol (PEG) 17 grams daily as first-line therapy, which has strong evidence for efficacy and safety with durable response over 6 months. 1

First-Line Treatment Approach

Polyethylene Glycol (PEG) - Preferred Initial Agent

• PEG is the recommended first-line osmotic laxative with moderate certainty evidence showing significant improvement in bowel movements (increases complete spontaneous bowel movements by 2.90 per week) 1
• Dosing: Start with 17 grams daily mixed in 8 ounces of liquid, titrate based on response with no clear maximum dose 1
• Cost-effective at $10-45 per month 1
• Common side effects include bloating, abdominal discomfort, and cramping, but generally well-tolerated 1
• Particularly recommended for elderly patients due to excellent safety profile 1

Alternative Osmotic Laxatives

• Lactulose (15 grams daily): Only osmotic agent studied in pregnancy, but bloating and flatulence may be limiting 1
• Magnesium oxide (400-500 mg daily): Use with extreme caution in renal impairment due to hypermagnesemia risk 1

Stimulant Laxatives - Short-Term or Rescue Therapy

Bisacodyl and sodium picosulfate are recommended for short-term use (≤4 weeks) or as rescue therapy, not as primary long-term management 1

• Bisacodyl: 5 mg daily, maximum 10 mg daily 1
• Senna: 8.6-17.2 mg daily, maximum 4 tablets twice daily 1
• Side effects include cramping, abdominal pain, and diarrhea 1
• Long-term safety and efficacy data are lacking 1

Fiber Supplementation - Mild Constipation Only

Fiber supplements can be considered for mild constipation before escalating to PEG, but psyllium requires adequate hydration 1

• Recommended dose: 14 grams per 1,000 kcal intake per day 1
• Critical caveat: Psyllium can cause intestinal obstruction if taken without adequate fluids (8-10 ounces per dose) 1, 2
• Avoid bulk laxatives in non-ambulatory patients with low fluid intake due to mechanical obstruction risk 1
• Not recommended for opioid-induced constipation 1

Advanced Therapies - When First-Line Fails

Intestinal Secretagogues

Consider these prescription agents when osmotic and stimulant laxatives fail:

• Lubiprostone 24 mcg twice daily: FDA-approved for chronic idiopathic constipation, may benefit abdominal pain 1, 3
• Linaclotide 72-145 mcg daily (maximum 290 mcg): May benefit abdominal pain 1
• Plecanatide 3 mg daily 1
• Cost: $374-563 per month 1
• Main side effect: diarrhea leading to discontinuation in some patients 1

Prokinetic Agent

• Prucalopride 1-2 mg daily: Serotonin-4 agonist, may help abdominal pain, but headaches and diarrhea can occur 1

Special Populations and Situations

Opioid-Induced Constipation

All patients on opioids should receive prophylactic laxatives unless contraindicated by pre-existing diarrhea 1

• First-line: Osmotic (PEG preferred) or stimulant laxatives 1
• Avoid bulk laxatives like psyllium 1
• If unresolved: Consider peripheral opioid antagonists (PAMORAs like methylnaltrexone or naloxegol) 1
• Combined opioid/naloxone formulations reduce OIC risk 1
• Lubiprostone is FDA-approved for opioid-induced constipation in chronic non-cancer pain (not effective for methadone) 3

Fecal Impaction

When digital rectal exam identifies full rectum or impaction, suppositories and enemas are first-line therapy 1

• Perform digital disimpaction followed by maintenance bowel regimen 1
• Contraindications to enemas: neutropenia, thrombocytopenia, paralytic ileus, recent colorectal/gynecological surgery, recent pelvic radiation 1

Elderly Patients

• PEG 17 grams daily is preferred due to safety profile 1
• Avoid liquid paraffin in bed-bound patients (aspiration pneumonia risk) 1
• Monitor for dehydration and electrolyte imbalances, especially with concurrent diuretics or cardiac glycosides 1

Critical Pitfalls to Avoid

• Never prescribe fiber supplements without emphasizing adequate fluid intake - can cause bowel obstruction 1, 2
• Avoid magnesium-based laxatives in renal impairment - hypermagnesemia risk 1
• Do not use stimulant laxatives as chronic daily therapy - reserve for short-term or rescue use 1
• Stool softeners alone (docusate) are ineffective - less effective than stimulant laxatives alone 1
• Assess for mechanical obstruction before treating - lubiprostone is contraindicated in bowel obstruction 3

Treatment Algorithm Summary

1. Mild constipation: Trial of fiber supplement (with adequate fluids) 1
2. Moderate constipation: PEG 17 grams daily 1
3. Inadequate response: Add or switch to lactulose, or add short-term stimulant laxative 1
4. Persistent symptoms: Consider intestinal secretagogues (lubiprostone, linaclotide, plecanatide) or prucalopride 1
5. Opioid-induced: Start prophylactic osmotic/stimulant laxative with opioid initiation; escalate to PAMORAs if needed 1
6. Impaction: Digital disimpaction, suppositories/enemas, then maintenance regimen 1