Treatment of Chronic Constipation
Start with fiber supplementation (particularly psyllium) for mild constipation, then escalate to polyethylene glycol (PEG) if fiber is insufficient, and reserve prescription agents like lubiprostone or prucalopride for refractory cases. 1, 2
Stepwise Treatment Algorithm
Step 1: Fiber Supplementation (First-Line)
- Psyllium is the preferred fiber supplement with the strongest evidence for effectiveness in chronic idiopathic constipation (CIC), though the overall certainty of evidence remains low 1, 2
- Start with at least 20-25g of total daily fiber intake, gradually increasing over several days to minimize bloating and flatulence 3
- Critical implementation point: Assess total dietary fiber intake before adding supplements to avoid unnecessary supplementation 1, 2
- Must be taken with 8-10 ounces of fluid to prevent worsening constipation 1
- Psyllium generally produces bowel movements in 12-72 hours 4
- Flatulence is the most common side effect 1
Common pitfall: Prescribing fiber without ensuring adequate hydration (at least 2 liters daily) can paradoxically worsen constipation 1, 5
Step 2: Polyethylene Glycol (PEG) - Osmotic Laxative
- PEG receives a strong recommendation when fiber is insufficient, with moderate certainty of evidence 1
- Dosing: 17g mixed in 8 ounces of liquid once daily 1
- Produces bowel movements in 1-3 days and has durable response over 6 months 1, 6
- PEG increases complete spontaneous bowel movements (CSBMs) by 2.90 per week and spontaneous bowel movements (SBMs) by 2.30 per week compared to placebo 1
- Side effects include abdominal distension, loose stool, flatulence, and nausea 1, 2
- Can be used in combination with fiber for additive effect 1
Step 3: Prescription Agents (Second-Line for Refractory Cases)
Lubiprostone (Prosecretory Agent)
- Conditional recommendation for adults with CIC who do not respond to over-the-counter agents, though evidence certainty is low 7
- Mechanism: Activates chloride channels in intestinal epithelium to enhance fluid secretion without directly stimulating smooth muscle 7
- Dosing: 24 mcg twice daily with food and water 7
- Nausea occurs in up to 30.9% of patients but is reduced when taken with food 7
- Monthly cost approximately $374 7
Stimulant Laxatives (Bisacodyl)
- Reserve for when first-line treatments fail 2
- Goal: One non-forced bowel movement every 1-2 days 2, 8
Prucalopride (5-HT4 Receptor Agonist)
Special Populations and Situations
Opioid-Induced Constipation
- Methylnaltrexone (peripherally acting μ-opioid receptor antagonist) relieves constipation while preserving pain management 2
- Dosing: 0.15 mg/kg subcutaneously every other day (maximum once daily) 8
- Absolute contraindications: Postoperative ileus or mechanical bowel obstruction 2, 8
Suspected Defecation Disorders
- Perform digital rectal examination to assess for dyssynergic defecation 9
- If suspected, obtain high-resolution anorectal manometry 9
- Anorectal biofeedback is effective for correcting pelvic floor dysfunction 9
Critical Assessment Points
Before Starting Treatment
- Rule out red flag symptoms requiring colonoscopy (rectal bleeding, unintentional weight loss, iron deficiency anemia) 9
- Screen for secondary causes: hypercalcemia, hypothyroidism, celiac disease 9
- Assess fluid intake—focus hydration efforts on those consuming <500 mL/day 1, 3
- Review medications that may cause constipation (opioids, anticholinergics, antipsychotics) 8
Lifestyle Modifications
- Evidence for increased water intake and exercise is weak except in specific populations (elderly, hospitalized, dehydrated, or those with very low baseline fluid intake <500 mL/day) 1, 3
- Daily 2 liters of water enhances fiber effects 5
- 30 minutes of exercise daily may alleviate symptoms 5