What are the treatment options for an adult patient with constipation and no significant medical history?

Treatment of Constipation in Adults

Start with polyethylene glycol (PEG) 17g daily as first-line 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

First-Line Pharmacological Treatment

• Polyethylene glycol (PEG) 17g once or twice daily is the preferred first-line agent with strong recommendation from both the American Gastroenterological Association and American College of Gastroenterology 1, 3
• PEG is inexpensive, widely available, well-tolerated, and effective for chronic idiopathic constipation 1
• Fiber supplementation receives only a conditional recommendation and should be increased slowly over several weeks to minimize bloating and gas 1
• Immediately discontinue docusate (stool softeners) as it provides no therapeutic benefit and has been proven less effective than stimulant laxatives alone 1, 2

Second-Line Treatment Options

For Rescue or Short-Term Use (≤4 weeks):

• Bisacodyl or sodium picosulfate are strongly recommended stimulant laxatives for breakthrough constipation 1, 3
• Senna receives only conditional recommendation 1

For Persistent Symptoms After 4-12 Weeks of PEG:

Secretagogues (Strong Recommendations):

• Linaclotide 145 mcg once daily is particularly effective when constipation is accompanied by significant abdominal pain or bloating, as it addresses both constipation and visceral pain 1, 2, 4
• Plecanatide is an alternative secretagogue with similar efficacy 1, 3
• Lubiprostone 24 mcg twice daily receives only conditional recommendation and requires dose adjustment in hepatic impairment 1, 5

Prokinetic Agent:

• Prucalopride 2 mg once daily is a selective 5-HT4 receptor agonist that enhances colonic motility through high-amplitude propagated contractions 1, 2, 3

Critical Exclusions Before Treatment

• Rule out mechanical bowel obstruction before initiating or escalating laxative therapy, especially with imaging showing fecal loading 2
• Check TSH to exclude hypothyroidism, a common reversible cause 2
• Measure serum calcium to rule out hypercalcemia 2
• Obtain basic metabolic panel to assess for hypokalemia 2
• Systematically review all medications for constipating effects including antacids, anticholinergics, and antiemetics 2

Special Considerations for Opioid-Induced Constipation

• All patients receiving opioid analgesics should be prescribed a concomitant laxative prophylactically unless contraindicated by pre-existing diarrhea 1
• Osmotic or stimulant laxatives are preferred for prophylaxis 1
• A stimulant laxative (such as senna) or PEG 17g twice daily with adequate fluid intake is recommended 1
• Bulk laxatives such as psyllium are not recommended for opioid-induced constipation and may worsen symptoms 1
• When response to laxatives is insufficient, peripherally acting mu-opioid receptor antagonists (PAMORAs) such as naloxegol or naldemedine can be added 1

When to Escalate Evaluation

• Perform anorectal testing in patients who do not respond to first-line laxatives to identify defecatory disorders such as dyssynergic defecation or pelvic floor dysfunction 2
• Biofeedback therapy is effective for dyssynergic defecation 6

Important Caveats

• Avoid magnesium-based laxatives in renal impairment due to risk of hypermagnesemia 1
• Enemas are contraindicated in patients with neutropenia, thrombocytopenia, recent colorectal surgery, or recent pelvic radiotherapy 1
• Avoid bulk agents in non-ambulatory patients with low fluid intake due to increased risk of mechanical obstruction 1
• Complete symptom resolution is often not achievable, and patients must understand that drug treatment is just one component of a multimodal approach 2
• The efficacy of all drugs for constipation is modest, with treatment differences typically around 1.5 complete spontaneous bowel movements per week compared to placebo 4