What is the recommended management for moderate constipation?

Management of Moderate Constipation

Start with polyethylene glycol (PEG) 17g daily as first-line pharmacological therapy for moderate constipation, as it has the strongest evidence base with moderate certainty and proven durability over 6 months. 1

Stepwise Treatment Algorithm

Step 1: Initial Pharmacological Management

Polyethylene glycol (PEG) is the preferred first-line agent for moderate constipation based on strong recommendations from the 2023 AGA-ACG guidelines. 1

• Dosing: Start with 17g mixed in 8 ounces of liquid once daily, taken on an empty stomach 1
• Efficacy: Increases complete spontaneous bowel movements by approximately 2.9 per week compared to placebo 2
• Cost: Approximately $10-45 per month, making it highly cost-effective 1
• Titration: Adjust dose based on symptom response and tolerability; no clear maximum dose exists 1
• Common side effects: Abdominal distension, loose stool, flatulence, and nausea 1
• Duration: Response has been shown to be durable over 6 months 1

Step 2: Alternative First-Line Options (If PEG Not Tolerated)

If PEG is not tolerated or contraindicated, consider these alternatives with conditional recommendations:

Magnesium oxide 1

• Dosing: 400-500mg daily (studies used 1,000-1,500mg daily) 1
• Cost: <$50 per month 1
• Caution: Use with extreme caution in patients with renal insufficiency and pregnancy 1

Lactulose 1

• Dosing: 15g daily 1
• Cost: <$50 per month 1
• Advantage: Only osmotic agent studied in pregnancy 1
• Limitation: Bloating and flatulence may be limiting, especially at higher doses 1

Step 3: Add Stimulant Laxatives for Inadequate Response

Sodium picosulfate or bisacodyl should be added if osmotic laxatives alone are insufficient. 1

• Bisacodyl dosing: Start 5mg daily, maximum 10mg orally daily 1
• Sodium picosulfate: Strong recommendation from 2023 guidelines 1
• Use pattern: Recommended for short-term use or rescue therapy 1
• Side effects: Cramping and abdominal discomfort; prolonged or excessive use can cause diarrhea and electrolyte disturbances 1
• Important note: Despite historical concerns, there is no evidence that stimulant laxatives at recommended doses are harmful to the colon, cause tolerance, or lead to "rebound constipation" 3

Step 4: Prescription Secretagogues and Prokinetics (Refractory Cases)

If over-the-counter agents fail, escalate to prescription medications with strong evidence:

Linaclotide (guanylate cyclase-C agonist) 1, 4

• Dosing: 145mcg orally once daily for chronic idiopathic constipation in adults 4
• Administration: Take on empty stomach at least 30 minutes before a meal 4
• Evidence: Strong recommendation with moderate certainty 1
• Side effect: Diarrhea is common 1, 4
• Contraindication: Patients less than 2 years of age due to risk of serious dehydration 4

Plecanatide (guanylate cyclase-C agonist) 1

• Strong recommendation from 2023 guidelines 1
• Diarrhea is a common side effect 1

Prucalopride (5-HT4 agonist/prokinetic) 1

• Strong recommendation from 2023 guidelines 1
• Particularly useful in slow-transit constipation 5

Lubiprostone (chloride channel activator) 1

• Conditional recommendation 1
• Less likely to cause diarrhea than guanylate cyclase-C agonists 1
• Warning: Nausea is a frequent side effect 1

Role of Fiber in Moderate Constipation

Fiber supplementation has only conditional recommendation and should NOT be the primary treatment for moderate constipation. 1

When Fiber May Be Appropriate:

• Mild constipation before escalating to PEG 1
• Combination therapy with PEG for added benefit 1
• Psyllium specifically has the best (though still low-quality) evidence among fiber types 1, 6, 2

Fiber Dosing and Precautions:

• Dose: 14g per 1,000 kcal intake per day, or 25g/day total 1, 2
• Hydration: Must take with at least 8-10 ounces of fluid 1, 6, 2
• Side effects: Bloating and abdominal discomfort are common 1

Critical Fiber Warnings:

• Avoid finely ground wheat bran powder as it can decrease stool water content and worsen constipation 1, 2
• Not appropriate for patients with inadequate fluid intake unless intake can be increased 2
• Not recommended for severely debilitated patients who cannot tolerate increased bulk 2
• Avoid in patients requiring rapid relief (fiber takes 2-3 days or longer for effect) 2
• Many patients with moderate-to-severe constipation experience worsening symptoms when increasing dietary fiber 3

Common Pitfalls to Avoid

Misconception About Fluid Intake:

• There is no evidence that increasing fluid intake treats constipation unless the patient is dehydrated 3
• Chronically constipated patients and non-constipated persons drink similar amounts of fluid daily 1
• Only patients in the lowest quartile for fluid intake benefit from increased fluids 1

Avoid Docusate:

• Docusate has inadequate experimental evidence and should not be recommended 2
• Fiber supplementation (particularly psyllium) should be used instead if a bulk agent is desired 2

Laxative Dependency Myths:

• Laxative dependence is NOT caused by prior laxative use; rather, some patients require laxatives for satisfactory bowel function due to their underlying condition 3
• Tolerance to stimulant laxatives is uncommon 3
• No evidence exists for "rebound constipation" after stopping laxatives 3

When to Pursue Further Evaluation

Perform anorectal testing if patients do not respond to over-the-counter osmotic and stimulant laxatives. 1, 7

Red Flags Requiring Assessment:

• Failure to respond to PEG plus stimulant laxatives 2
• Assess for fecal impaction, obstruction, hypercalcemia, hypokalemia, hypothyroidism, or diabetes 2
• Consider defecatory disorders (dyssynergic defecation) requiring biofeedback therapy 1, 7
• Evaluate for slow-transit constipation with colonic transit studies 7, 5

Specialized Testing:

• Biofeedback therapy is the treatment of choice for defecatory disorders, with >70% improvement rates 1
• Colonic manometry and barostat testing for patients not responding to standard approaches 1, 7

Cost-Effectiveness Considerations

The treatment algorithm prioritizes cost-effectiveness: 8

• PEG costs approximately $1 per day versus $7-9 per day for newer prescription agents like linaclotide and lubiprostone 1
• Lifestyle advice, dietary treatments, and PEG are all cost-effective compared to newer agents 8
• Reserve expensive prescription medications for patients who fail over-the-counter therapies 8