What medication is prescribed for a patient with constipation?

Medication Management for Constipation

For general constipation, prescribe osmotic laxatives (polyethylene glycol/PEG or lactulose) or stimulant laxatives (senna, bisacodyl, or sodium picosulfate) as first-line pharmacologic therapy. 1

First-Line Medication Options

Osmotic Laxatives (Preferred)

• Polyethylene glycol (PEG) is the most evidence-based choice, with a recommended dose of 17 g once daily mixed with 8 oz of water 1
• PEG demonstrates superior efficacy with 52% treatment success versus 11% for placebo over 6 months, and is safe for long-term use 2
• For elderly patients specifically, PEG 17 g/day offers an efficacious and tolerable solution with a good safety profile 1
• Lactulose 30-60 mL twice to four times daily is an alternative osmotic option 1
• Magnesium-based salts (magnesium hydroxide 30-60 mL daily or magnesium citrate 8 oz daily) can be used, but exercise caution in renal impairment due to hypermagnesemia risk 1

Stimulant Laxatives

• Senna with or without docusate: 2-3 tablets twice to three times daily, titrating to achieve one non-forced bowel movement every 1-2 days 1
• Bisacodyl 10-15 mg orally 2-3 times daily, or as a rectal suppository once daily 1
• Sodium picosulfate is another stimulant option 1

Important caveat: Stool softeners (docusate) alone are less effective than stimulant laxatives and should not be used as monotherapy 1

Medication Selection Algorithm

Step 1: Initial Assessment

• Rule out fecal impaction via digital rectal exam—if present, use suppositories/enemas first, then oral laxatives 1
• Rule out bowel obstruction via physical exam and plain abdominal X-ray if clinically indicated 1
• Identify if constipation is opioid-induced, as this requires specific management 1

Step 2: Choose First-Line Agent

• Start with PEG 17 g daily for most patients due to superior evidence, safety profile, and once-daily dosing 2, 3
• Consider stimulant laxatives (senna or bisacodyl) as equally valid first-line alternatives 1
• Avoid bulk laxatives (psyllium) in patients with limited mobility or low fluid intake, as they increase impaction risk 1

Step 3: Titration and Monitoring

• Goal: One non-forced bowel movement every 1-2 days 1
• If inadequate response after 1 week, add a second agent from a different class (e.g., add stimulant to osmotic) 1
• For persistent constipation, consider adding rectal bisacodyl suppository, lactulose, or magnesium hydroxide 1

Special Populations and Situations

Opioid-Induced Constipation (OIC)

• All patients on opioids should receive prophylactic laxatives unless contraindicated by pre-existing diarrhea 1
• First-line: Osmotic (PEG) or stimulant laxatives (senna, bisacodyl) 1
• Avoid bulk laxatives (psyllium) for OIC—they are ineffective 1
• For refractory OIC, consider methylnaltrexone 0.15 mg/kg subcutaneously every other day (maximum once daily), a peripherally-acting μ-opioid receptor antagonist 1
• Combined opioid/naloxone formulations reduce OIC risk 1

Elderly Patients

• PEG 17 g/day is preferred due to excellent safety profile and efficacy in this population 1
• Avoid liquid paraffin in bed-bound patients or those with swallowing disorders (aspiration pneumonia risk) 1
• Use magnesium-based laxatives cautiously due to hypermagnesemia risk, especially with concurrent diuretics or cardiac glycosides 1
• Monitor for dehydration and electrolyte imbalances, particularly with heart or kidney failure 1

Medication-Induced Constipation (Non-Opioid)

• PEG 17 g daily demonstrates 78.3% treatment success versus 39.1% for placebo in patients taking constipating medications 4
• Same first-line approach as general constipation 4

Refractory Constipation

For patients failing first-line osmotic and stimulant laxatives:

• Linaclotide (guanylate cyclase-C agonist) is FDA-approved for chronic idiopathic constipation and IBS-C in adults, and functional constipation in pediatric patients 6-17 years 5
• Prucalopride (5-HT4 receptor agonist) 2 mg orally once daily for refractory cases, though significantly more expensive (~$563/month) 6
• Consider prokinetic agents like metoclopramide 10-20 mg four times daily if gastroparesis is suspected 1

Critical Contraindications and Warnings

Enema Contraindications

Enemas are contraindicated in: 1

• Neutropenia or thrombocytopenia
• Paralytic ileus or intestinal obstruction
• Recent colorectal/gynecological surgery
• Recent anal or rectal trauma
• Severe colitis, abdominal inflammation/infection
• Toxic megacolon
• Undiagnosed abdominal pain
• Recent pelvic radiotherapy

Medication-Specific Cautions

• Magnesium salts: Risk of hypermagnesemia in renal impairment 1
• Linaclotide: Contraindicated in children <2 years (severe diarrhea/dehydration risk); contraindicated in bowel obstruction 5
• Methylnaltrexone: Do not use in postoperative ileus or mechanical bowel obstruction 1

Adjunctive Non-Pharmacologic Measures

While medications are the focus, combine with: 1

• Increased fluid intake
• Increased activity/mobility within patient limits
• Privacy and proper positioning for defecation (footstool to assist)
• Abdominal massage (particularly beneficial in neurogenic constipation) 1