What are the recommended guidelines for evaluating and treating constipation, including lifestyle measures, medication options, red‑flag assessment, and special considerations for elderly or opioid‑using patients?

Guidelines for Treating Constipation

Start polyethylene glycol (PEG) 17 g twice daily (34 g total) as first-line therapy for constipation, and if no bowel movement occurs within 24-48 hours, add bisacodyl 10-15 mg daily. 1, 2, 3

Initial Assessment and Red Flags

Before initiating treatment, perform a digital rectal examination to rule out fecal impaction and bowel obstruction—these conditions require immediate intervention rather than escalating oral laxatives. 1, 2 If the rectum is full or impacted, proceed directly to manual disimpaction (digital fragmentation and extraction after pre-medication with analgesic ± anxiolytic) or use suppositories/enemas as first-line therapy rather than oral agents. 1, 2

Rule out bowel obstruction before escalating any laxative therapy, particularly if symptoms worsen despite treatment. 1, 3 Imaging may be useful to assess the extent of fecal loading and exclude obstruction. 1

Non-Pharmacological Measures (Implement First)

• Ensure adequate toilet access, especially critical for patients with decreased mobility—this single intervention prevents recurrence and is often overlooked. 1, 2, 4

• Optimize toileting habits: educate patients to attempt defecation twice daily, 30 minutes after meals, straining no more than 5 minutes. 1, 2, 4

• Increase fluid intake to at least 1.5 liters daily within patient limits. 1, 2, 4

• Encourage physical activity and increased mobility as tolerated, even bed-to-chair transfers. 1

• Provide dietetic support to manage decreased food intake from anorexia, chewing difficulties, or other causes that negatively influence stool volume and consistency. 1, 2

• Abdominal massage can reduce gastrointestinal symptoms and improve bowel efficiency, particularly in patients with concomitant neurogenic problems. 1

First-Line Pharmacological Treatment

PEG 17 g mixed with 8 oz water twice daily (34 g total/day) is the preferred first-line agent due to virtually no net electrolyte disturbance, proven safety for continuous use beyond 12 months, and superior efficacy across all patient populations. 1, 2, 4, 3 This recommendation is stronger than using stimulant laxatives alone because PEG has the strongest safety profile for long-term use. 3

Alternative osmotic laxatives include lactulose 30-60 mL daily or sorbitol 30 mL every 2 hours × 3 doses, though PEG is preferred. 1, 2

Second-Line: Add Stimulant Laxatives

If constipation persists after 24-48 hours of PEG therapy, add bisacodyl 10-15 mg daily (maximum 10 mg orally for regular use). 1, 3 Alternatively, use senna 2 tablets every morning with a maximum of 8-12 tablets per day. 1, 3

The goal is one non-forced bowel movement every 1-2 days. 1, 3

Opioid-Induced Constipation (Special Considerations)

All patients receiving opioid analgesics must be prescribed a prophylactic laxative at initiation of opioid therapy unless contraindicated by pre-existing diarrhea—never wait for constipation to develop. 1, 2, 3 This is non-negotiable because opioid-induced constipation is nearly universal and causes patients to skip pain medications. 5, 6

• Prophylactic regimen: Start either PEG 17 g twice daily or a stimulant laxative (senna 2 tablets every morning or bisacodyl 10 mg daily) at opioid initiation. 1, 3

• Increase laxative dose when increasing opioid dose to maintain bowel function. 1

• Bulk laxatives such as psyllium are not recommended for opioid-induced constipation because they do not target the underlying mechanism (peripheral μ-opioid receptor blockade) and may worsen obstruction. 1, 7, 8

• If first-line laxatives fail after adequate trial, consider peripherally acting μ-opioid receptor antagonists (PAMORAs) such as methylnaltrexone 0.15 mg/kg subcutaneously (maximum dose per day), naloxegol, or naldemedine. 1, 7, 8, 9 These agents reduce peripheral opioid effects without diminishing analgesia or inducing central withdrawal. 8, 9

• Combined opioid/naloxone medications reduce the risk of opioid-induced constipation through phase II and III studies. 1

Persistent Constipation: Third-Line Options

If constipation persists despite optimized PEG and stimulant laxatives:

• Reassess for cause and severity; rule out bowel obstruction and check for impaction via digital rectal examination. 1, 2, 3

• Add magnesium hydroxide 30-60 mL daily for rapid bowel evacuation, but only after confirming normal renal function due to hypermagnesemia risk. 1, 3 Magnesium and sulfate salts should be used cautiously in any degree of renal impairment. 1, 2, 4

• Consider metoclopramide 10-20 mg PO four times daily as a prokinetic agent to enhance gastric antral contractility, though chronic use carries tardive dyskinesia risk. 1, 3

• Magnesium citrate or polyethylene glycol (higher dose) can be used for more aggressive bowel preparation. 1

• Fleet, saline, or tap water enema may be necessary for rectal clearance. 1

Management of Fecal Impaction

• Manual disimpaction (digital fragmentation and extraction) is best practice in the absence of suspected perforation or bleed, followed by implementation of a maintenance bowel regimen to prevent recurrence. 1, 2

• Suppositories (bisacodyl) or enemas are preferred first-line therapy when digital rectal examination identifies a full rectum or fecal impaction. 1, 2

• Use isotonic saline enemas (500-1000 mL) rather than sodium phosphate enemas in elderly patients due to fewer adverse effects. 2, 4

• Enemas are contraindicated in patients with neutropenia, thrombocytopenia, paralytic ileus, intestinal obstruction, recent colorectal or gynecological surgery, recent anal or rectal trauma, severe colitis, inflammation or infection of the abdomen, toxic megacolon, undiagnosed abdominal pain, or recent pelvic radiotherapy. 1

Special Considerations for Elderly Patients

Elderly patients require particular attention due to multiple comorbidities, polypharmacy, and increased risk of adverse effects. 1, 2

• PEG 17 g/day offers an efficacious and tolerable solution with a good safety profile for elderly patients. 1, 2, 4

• Laxatives must be individualized based on cardiac and renal comorbidities, drug interactions, and adverse effects. 1, 2, 4

• Regular monitoring is essential for chronic kidney/heart failure when concomitant treatment with diuretics or cardiac glycosides is prescribed due to risk of dehydration and electrolyte imbalances. 1

• Review and withdraw inappropriate or unnecessary constipating medications (anticholinergics, antipsychotics like quetiapine, calcium channel blockers, iron supplements). 2, 4

Critical Pitfalls to Avoid

• Never use stool softeners (docusate) alone without stimulant or osmotic laxatives—they lack efficacy for medication-induced constipation and are ineffective compared to PEG or stimulant laxatives. 2, 4, 3

• Never use bulk-forming laxatives (psyllium, methylcellulose) in non-ambulatory patients with low fluid intake due to increased risk of mechanical obstruction. 1, 2, 4

• Avoid liquid paraffin in bed-bound patients and those with swallowing disorders due to risk of aspiration lipoid pneumonia. 1, 2, 4

• Avoid magnesium-containing laxatives in patients with any degree of renal impairment due to hypermagnesemia risk. 1, 2, 4, 3

• Never wait for constipation to develop before starting laxatives in patients on opioids or antipsychotics—this causes unnecessary suffering and can lead to paralytic ileus. 3

• Always rule out bowel obstruction before escalating laxative therapy, particularly if symptoms worsen despite treatment. 1, 3