Treatment Plan for Chronic Constipation
Start with polyethylene glycol (PEG) 17 g daily as first-line pharmacological therapy for chronic idiopathic constipation, as it has the strongest evidence for efficacy with moderate certainty and durable response over 6 months. 1
Stepwise Treatment Algorithm
Step 1: Initial Therapy
Fiber supplementation can be considered as initial therapy, particularly in patients with low dietary fiber intake and mild-to-moderate symptoms 1:
- Psyllium is the only fiber with reasonable evidence of efficacy (though still low quality) 1, 2
- Dose: 14 g per 1,000 kcal intake per day 1
- Requires adequate hydration (8-10 ounces of fluid with each dose) 1
- Most effective at doses >10 g/day for at least 4 weeks 2
- Common side effect: flatulence and bloating 1, 2
However, proceed directly to PEG if symptoms are moderate-to-severe, as fiber has only conditional recommendation with low certainty evidence 1
Step 2: First-Line Pharmacological Therapy
Polyethylene glycol (PEG) - Strong recommendation with moderate certainty 1:
- Dose: 17 g daily mixed in 8 ounces of liquid 1
- Increases complete spontaneous bowel movements by 2.9 per week 1
- Increases spontaneous bowel movements by 2.3 per week 1
- Response is durable over 6 months 1
- Side effects: bloating, abdominal discomfort, cramping, loose stools 1
- Cost: $10-45/month 1
Alternative osmotic laxatives if PEG not tolerated 1:
- Magnesium oxide: 400-500 mg daily (caution in renal insufficiency and pregnancy) 1
- Lactulose: 15 g daily (only osmotic agent studied in pregnancy; may cause limiting flatulence) 1
Step 3: Rescue or Short-Term Therapy
Stimulant laxatives for short-term use or rescue therapy 1:
- Bisacodyl: 5 mg daily (maximum 10 mg daily) 1
- Senna: 8.6-17.2 mg daily 1
- Important caveat: Long-term safety and efficacy unknown; prolonged use can cause diarrhea and electrolyte imbalance 1
- Recommended for intermittent use, not continuous therapy 1
Step 4: Second-Line Prescription Agents
If inadequate response to PEG after appropriate trial, escalate to prescription secretagogues or prokinetics 1:
Intestinal secretagogues:
Prokinetic agent:
- Prucalopride: 1-2 mg daily (maximum 2 mg daily) 1
Step 5: Specialized Evaluation
If refractory to pharmacological therapy, evaluate for defecatory disorders with anorectal testing 4:
- Anorectal manometry
- Balloon expulsion test
- Defecography
- Pelvic floor biofeedback therapy if dyssynergic defecation identified 5, 4
Assess colonic transit if normal defecatory function 4:
- Radiopaque markers or wireless motility capsule
- Consider colonic manometry if slow transit confirmed 4
Dose Titration Strategy
All medications should be titrated based on symptom response and side effects 1:
- Start at recommended initial dose
- Increase gradually if inadequate response after 1-2 weeks
- Most agents have no clear maximum dose except bisacodyl (10 mg daily) and prucalopride (2 mg daily) 1
Critical Pitfalls to Avoid
Do not rely on stimulant laxatives as chronic therapy - long-term safety unknown and risk of electrolyte imbalance with prolonged use 1
Ensure adequate hydration with fiber supplementation - fiber without adequate fluid can worsen constipation 1
Screen for secondary causes before labeling as chronic idiopathic constipation: medications (especially opioids), metabolic disorders (hypothyroidism, hypercalcemia, diabetes), and anatomic obstruction 1, 4
For opioid-induced constipation specifically, consider peripherally-acting μ-opioid receptor antagonists (methylnaltrexone, naloxegol) rather than standard laxatives 1
Wheat bran may worsen symptoms - finely ground powder can decrease stool water content and harden stool 1
Special Populations
Pregnancy: Lactulose is the only osmotic agent studied in pregnancy; use magnesium oxide with caution 1
Renal insufficiency: Avoid or use magnesium-containing laxatives with extreme caution 1
Pediatric patients 6-17 years: Linaclotide is FDA-approved for functional constipation in this age group 3