What are the guidelines for managing functional constipation?

Guidelines for Functional Constipation Management

First-Line Treatment: Polyethylene Glycol

The American Gastroenterological Association and American College of Gastroenterology strongly recommend polyethylene glycol (PEG) 17g daily as the first-line pharmacological treatment for chronic idiopathic constipation in adults. 1, 2, 3

• PEG increases complete spontaneous bowel movements by approximately 2.9 per week compared to placebo, with durable response over 6 months 2
• Administer 17g dissolved in 8 ounces of liquid once daily, taken with food and water 2, 4
• Common side effects include abdominal distension, loose stool, flatulence, and nausea 2

Non-Pharmacological Interventions (Implement Simultaneously)

All patients should receive comprehensive lifestyle modifications alongside pharmacological therapy:

• Hydration: Increase fluid intake to at least 1.5 liters daily 3
• Dietary fiber: Target 14g fiber per 1,000 kcal intake daily 3, 5
• Physical activity: Increase mobility and exercise within patient limits, even bed-to-chair transfers 1, 3
• Toileting habits: Establish regular attempts twice daily, preferably 30 minutes after meals; use a small footstool to assist gravity and proper positioning; ensure privacy and comfort 1, 3, 5
• Strain no more than 5 minutes per attempt 1

Fiber Supplementation

The AGA/ACG conditionally recommend fiber supplementation, with psyllium having the best evidence for efficacy 1, 2:

• Most beneficial for mild-to-moderate symptoms, especially in patients with fiber-deficient diets 2
• Titrate dose based on symptom response and side effects 5
• Critical caveat: Never increase fiber without ensuring adequate hydration, as this can worsen constipation 5
• Common side effect is flatulence 2
• Avoid bulk laxatives in non-ambulatory patients with low fluid intake due to risk of mechanical obstruction 1, 3

Second-Line Pharmacological Options

Osmotic Laxatives (After PEG)

• Lactulose: 15g daily; may cause bloating and flatulence but is the only osmotic agent studied in pregnancy 5
• Magnesium oxide: 400-500mg daily; use with extreme caution in renal impairment due to hypermagnesemia risk 1, 5

Stimulant Laxatives

The AGA/ACG strongly recommend sodium picosulfate and conditionally recommend senna for chronic idiopathic constipation 1, 2:

• Senna: 8.6-17.2mg daily 5
• Bisacodyl: 5mg daily (maximum 10mg daily) 5
• Reserve primarily for short-term use or rescue therapy due to potential for cramping, abdominal discomfort, and electrolyte imbalance with prolonged use 5
• Exception: Prophylactic stimulant laxatives are strongly recommended for opioid-induced constipation 3, 5

Prescription Medications for Refractory Cases

Secretagogues (Strong Recommendations)

The AGA/ACG strongly recommend the following for patients not responding to over-the-counter options 1, 2:

• Linaclotide: Chloride channel activator 1
• Plecanatide: Guanylate cyclase-C agonist 1

Prokinetic Agent (Strong Recommendation)

• Prucalopride: 2mg once daily (reduce to 1mg daily in severe renal impairment with CrCL <30 mL/min) 1, 2, 6
• Trial duration in studies was 4-24 weeks 5
• Side effects include headache, abdominal pain, nausea, and diarrhea 5, 6
• Monitor for suicidal ideation and behavior; instruct patients to discontinue immediately if unusual mood changes or suicidal thoughts occur 6

Chloride Channel Activator (Conditional Recommendation)

• Lubiprostone: 24 mcg twice daily for chronic idiopathic constipation 1, 4
• Take with food and water; swallow whole, do not break or chew 4
• Contraindicated in mechanical gastrointestinal obstruction 4
• May cause nausea (reduced by taking with food), diarrhea, dyspnea within first hour, and syncope/hypotension 4

Special Populations and Situations

Opioid-Induced Constipation

All patients receiving opioid analgesics should be prescribed a concomitant laxative prophylactically unless contraindicated by pre-existing diarrhea 1:

• First-line: Osmotic or stimulant laxatives 1, 3
• Never use bulk laxatives (psyllium) for opioid-induced constipation 1, 3, 5
• For persistent opioid-induced constipation despite laxatives, consider peripherally acting μ-opioid antagonists (PAMORAs) such as methylnaltrexone 1, 2
• Combined opioid/naloxone medications reduce risk of opioid-induced constipation 1

Elderly Patients

• PEG 17g daily offers optimal efficacy and tolerability with good safety profile 1, 3
• Ensure access to toilets, especially with decreased mobility 1
• Provide dietetic support and manage decreased food intake 1
• Avoid liquid paraffin in bed-bound patients and those with swallowing disorders due to aspiration lipoid pneumonia risk 1
• Avoid saline laxatives (magnesium hydroxide) due to hypermagnesemia risk 1
• Avoid non-absorbable soluble fiber or bulk agents in non-ambulatory patients with low fluid intake 1
• Regular monitoring required when diuretics or cardiac glycosides are co-prescribed (risk of dehydration and electrolyte imbalances) 1

Fecal Impaction

When digital rectal examination identifies full rectum or fecal impaction 1, 3:

• Suppositories and enemas are preferred first-line therapy 1, 3
• Glycerin suppositories or manual disimpaction (digital fragmentation and extraction) 1, 5
• Isotonic saline enemas are preferable in older adults 1
• Enemas are contraindicated in: neutropenia, thrombocytopenia, paralytic ileus, intestinal obstruction, recent colorectal/gynecological surgery, recent anal/rectal trauma, severe colitis, abdominal inflammation/infection, toxic megacolon, undiagnosed abdominal pain, or recent pelvic radiotherapy 1, 5

Treatment Algorithm

1. Initiate simultaneously: All non-pharmacological measures (hydration, fiber, mobility, toileting habits) 3
2. Add PEG 17g daily as first-line pharmacological therapy 1, 2, 3
3. If rectal fullness on digital rectal examination: Use suppositories or enemas 3, 5
4. If inadequate response to PEG: Add or switch to lactulose, magnesium oxide, or stimulant laxatives (senna, bisacodyl) 2, 5
5. For refractory cases: Escalate to prescription secretagogues (linaclotide, plecanatide) or prokinetic agent (prucalopride) 1, 2
6. Assess periodically the need for continuous therapy 4

Critical Pitfalls to Avoid

• Never increase fiber without ensuring adequate hydration 5
• Never use bulk laxatives for opioid-induced constipation 1, 3, 5
• Never delay prophylactic laxatives when initiating opioids 3, 5
• Never use magnesium-containing laxatives without considering renal function 1, 5
• Avoid inadequate trial periods before escalating therapy 2
• Never use enemas in neutropenic, thrombocytopenic, or post-surgical patients 1, 5