What is the recommended medication regimen for treating constipation in an elderly patient, including first‑line and second‑line options and considerations for comorbidities?

Medication for Constipation in Elderly Patients

First-Line Pharmacological Treatment

Polyethylene glycol (PEG) 17 g once daily is the preferred first-line medication for elderly patients with constipation due to its excellent safety profile, efficacy, and lack of electrolyte disturbances even in patients with cardiac or renal failure. 1, 2

• PEG demonstrates superior tolerability compared to other laxative classes and can be safely used long-term without causing electrolyte imbalances, making it ideal for elderly patients with multiple comorbidities 1, 2
• If no bowel movement occurs within 3-4 days, escalate to PEG 17 g twice daily (34 g total per day) 1
• The goal is to achieve one non-forced bowel movement every 1-2 days 2

Second-Line Options: Adding Stimulant Laxatives

If PEG alone remains ineffective after 3-4 days at the escalated dose, add a stimulant laxative as adjunctive therapy:

• Bisacodyl 10-15 mg orally once daily is the preferred stimulant addition 1, 2
• Senna (2 tablets every morning, maximum 8-12 tablets daily) is an effective alternative stimulant 2
• Stimulant laxatives may cause cramping and abdominal pain, which should be discussed with patients 1

Alternative Osmotic Laxatives

When PEG is not tolerated or unavailable:

• Lactulose 30-60 mL twice to four times daily can be used as an alternative osmotic agent 1
• Lactulose may cause bloating and flatulence, which can limit adherence in some patients 1

Critical Safety Considerations and Contraindications

Agents to Avoid in Elderly Patients

• Bulk-forming laxatives (psyllium, methylcellulose) are contraindicated in non-ambulatory elderly patients with low fluid intake due to high risk of mechanical bowel obstruction 3, 1, 4
• Magnesium-containing laxatives (magnesium hydroxide, magnesium citrate) must be avoided in any degree of renal impairment due to serious hypermagnesemia risk 3, 1, 4, 2
• Liquid paraffin should never be used in bed-bound patients or those with swallowing disorders due to aspiration lipoid pneumonia risk 3, 1
• Docusate alone lacks efficacy for medication-induced constipation and should be reserved only for very specific situations where other options are contraindicated 1, 2

Monitoring Requirements

• Regular monitoring is essential for elderly patients on concurrent diuretics or cardiac glycosides, as laxatives can amplify risks of dehydration and electrolyte imbalances 3, 1
• Always confirm normal renal function before prescribing any magnesium-based laxative 1, 2

Management of Fecal Impaction

When digital rectal examination identifies a full rectum or fecal impaction:

• Manual disimpaction (digital fragmentation and extraction) is first-line therapy after pre-medication with analgesia ± anxiolysis 3, 1
• Isotonic saline enemas (500-1000 mL) are preferred over sodium phosphate enemas due to fewer adverse effects and lower risk of electrolyte disturbances in elderly patients 1, 4
• Suppositories or enemas should be used as first-line treatment when impaction is confirmed 3, 4
• After successful disimpaction, immediately initiate PEG 17 g daily as maintenance therapy to prevent recurrence 1

Enema Contraindications

Enemas are absolutely contraindicated in patients with: neutropenia, thrombocytopenia, paralytic ileus, intestinal obstruction, recent colorectal or gynecological surgery, recent anal or rectal trauma, severe colitis, toxic megacolon, undiagnosed abdominal pain, or recent pelvic radiotherapy 3, 4

Opioid-Induced Constipation

All elderly patients receiving opioid analgesics must be prescribed prophylactic laxatives at the time of opioid initiation, unless contraindicated by pre-existing diarrhea. 3, 1, 2

• Osmotic laxatives (PEG) or stimulant laxatives (senna, bisacodyl) are preferred for opioid-induced constipation 3, 1
• Bulk laxatives such as psyllium are not recommended for opioid-induced constipation 3
• Peripherally acting mu-opioid receptor antagonists (PAMORAs) can be considered for unresolved opioid-induced constipation that does not respond to standard laxatives, though they are costly 1, 5

Essential Non-Pharmacological Measures

Before and alongside pharmacological treatment, implement these evidence-based interventions:

• Ensure easy toilet access, especially for patients with decreased mobility, as this single environmental modification markedly reduces constipation recurrence 3, 1
• Optimize toileting habits: educate patients to attempt defecation twice daily, 30 minutes after meals, straining no more than 5 minutes 3, 1
• Provide dietetic support to manage decreased food intake from age-related anorexia or chewing difficulties 3, 1
• Encourage any tolerated physical activity (even bed-to-chair transfers) to improve bowel motility 3, 1
• Increase fluid intake to at least 1.5 liters daily within patient limits 1

Individualization Based on Comorbidities

Laxative selection must be tailored to the elderly patient's specific medical history:

• Cardiac comorbidities: PEG is safe and does not cause electrolyte disturbances that could affect cardiac function 1
• Renal impairment: Avoid all magnesium-containing laxatives; PEG remains safe 3, 1, 2
• Dysphagia or swallowing difficulties: Prioritize rectal therapies (suppositories or isotonic saline enemas) over oral agents 1, 4
• Limited mobility: Avoid bulk-forming laxatives entirely due to obstruction risk 3, 1, 4

Common Pitfalls to Avoid

• Never wait for constipation to develop before starting prophylactic laxatives in patients on opioids or other constipating medications 2
• Never prescribe fiber supplements to elderly patients with limited mobility or inadequate fluid intake, as this may exacerbate obstruction 1
• Never use stool softeners alone without stimulant or osmotic laxatives for medication-induced constipation 2
• Always perform digital rectal examination before escalating laxative therapy to rule out fecal impaction or bowel obstruction 1, 2