How should chronic constipation be managed in a middle‑aged adult?

Management of Chronic Constipation in Middle-Aged Adults

Start with polyethylene glycol (PEG) 17g daily as first-line pharmacological therapy, and if symptoms persist after 4-12 weeks, escalate to prescription secretagogues (linaclotide 145 mcg or plecanatide) or the prokinetic prucalopride rather than continuing to increase laxative doses. 1, 2

Initial Approach: Lifestyle Modifications Before Medications

Before starting pharmacological therapy, implement dietary modifications including increased fluid intake and dietary fiber, along with behavioral changes such as regular exercise and scheduled toileting after meals. 2 However, recognize that while these are recommended first steps, the clinical evidence supporting their effectiveness in chronic constipation is limited. 3, 4

First-Line Pharmacological Treatment Algorithm

Step 1: Polyethylene Glycol (PEG)

PEG receives a strong recommendation with moderate-quality evidence as the optimal first-line agent. 1

• Start at 17g daily and continue for 4-12 weeks before considering escalation 2
• PEG demonstrates durable response over 6 months 1
• Side effects include abdominal distension, loose stool, flatulence, and nausea 1
• PEG is inexpensive, widely available, and well-tolerated, making it the optimal first-line choice 2

Step 1 Alternative: Fiber Supplementation (Conditional Recommendation)

For patients with low dietary fiber intake or mild constipation, psyllium can be used as first-line therapy or in combination with PEG. 1 However, only psyllium has evidence of effectiveness—data on bran and inulin are very limited and uncertain. 1 Adequate hydration must be encouraged with fiber use, and flatulence is a common side effect. 1

Second-Line Treatment: Prescription Agents (After 4-12 Weeks of PEG)

Critical pitfall to avoid: Do not continue escalating osmotic laxative doses indefinitely—switch to prescription agents after 4-12 weeks if inadequate response. 2, 5

Prescription Secretagogues (Strong Recommendations)

Linaclotide 145 mcg once daily receives a strong recommendation for chronic idiopathic constipation. 1, 2

• In clinical trials, 20% of patients on linaclotide 145 mcg were CSBM responders (≥3 complete spontaneous bowel movements and increase ≥1 from baseline) for at least 9 out of 12 weeks, compared to 3-6% on placebo 6
• Improvements in stool frequency reached maximum level during week 1 and were maintained over 12 weeks 6
• For constipation with significant abdominal pain/bloating, linaclotide is superior to osmotic laxatives for addressing both constipation and visceral pain 5

Plecanatide receives a strong recommendation as an alternative secretagogue with a similar mechanism to linaclotide. 1, 2

Lubiprostone 24 mcg twice daily receives a conditional recommendation with lower-quality evidence. 1, 2

• In clinical trials, 27.1% of patients on lubiprostone were "overall responders" compared to 18.9% on placebo 7
• Demonstrated increases in percentage of patients with spontaneous bowel movements within first 24 hours (57-63% vs. 32-37% on placebo) 7

Prokinetic Agent (Strong Recommendation)

Prucalopride (serotonin type 4 agonist) receives a strong recommendation for chronic idiopathic constipation. 1, 2

• Prucalopride 2 mg once daily is a selective 5-HT4 receptor agonist that enhances colonic motility through high-amplitude propagated contractions 5
• Particularly useful for severe motility dysfunction 5

Rescue and Short-Term Therapy

Bisacodyl or sodium picosulfate receive strong recommendations for short-term use (≤4 weeks) or rescue therapy. 1, 2

• Short-term use is defined as daily use for 4 weeks or less 1
• This is a good option for occasional use or rescue therapy in combination with other pharmacological agents 1
• While long-term use is probably appropriate, data are needed to better understand tolerance and side effects 1

Senna receives a conditional recommendation with low-quality evidence. 1, 2

Alternative Osmotic Laxatives (Conditional Recommendations)

Magnesium oxide receives a conditional recommendation with very low-quality evidence. 1

• Critical caveat: Avoid use in patients with renal insufficiency due to risk of hypermagnesemia—check creatinine clearance before prescribing 1, 2
• Start at a lower dose, which may be increased if necessary 1

Lactulose receives a conditional recommendation for patients who fail or are intolerant to over-the-counter therapies. 1

• Bloating and flatulence are dose-dependent and common side effects, which may limit its use in clinical practice 1

When to Escalate or Refer

Confirming Adequate Trial Before Switching

Confirm adequate trial of current medications for at least 4 weeks before switching. 2 If PEG is inadequate after 4-6 weeks, add or switch to a prescription secretagogue. 2

Red Flags Requiring Urgent Evaluation

Rule out mechanical bowel obstruction before escalating laxative therapy, particularly with prominent fecal loading on imaging. 2, 5 The combination of left lower quadrant pain, nausea, and severe constipation warrants consideration of impaction requiring manual disimpaction or glycerin suppositories. 5

Referral to Gastroenterology

Refer patients to gastroenterology for anorectal manometry and balloon expulsion test if initial treatment approach is ineffective. 8, 9 This identifies defecatory disorders (dyssynergic defecation, pelvic floor dysfunction) that may respond to biofeedback therapy. 8, 9 Patients in whom pelvic floor dysfunction is identified early should be referred for pelvic floor therapy with biofeedback while first-line medications are initiated. 8

Secondary Causes to Exclude

Before escalating therapy, rule out reversible secondary causes:

• Hypothyroidism: Check TSH 5
• Hypercalcemia: Check serum calcium 5
• Hypokalemia: Check basic metabolic panel 5
• Diabetes mellitus: Can cause autonomic neuropathy affecting gut motility 5
• Medications: Systematically review all medications for constipating effects, including antacids, anticholinergic drugs, and antiemetics 5

Important Clinical Considerations

Discontinue docusate immediately—it provides no therapeutic benefit and has been shown to be less effective than stimulant laxatives alone. 5

Complete symptom resolution is often not achievable, and patients must understand that drug treatment is just one component of a multimodal approach, with the efficacy of all drugs for constipation being modest. 5 The 2023 AGA-ACG guidelines used the GRADE Evidence to Decision framework, which considered costs and health equity in formulating recommendations. 2

Prescription secretagogues and prokinetics are more expensive than PEG but have strong evidence for efficacy when over-the-counter agents fail. 2