Management of Acute Constipation in Adults
Start with polyethylene glycol (PEG) 17g mixed in 8 oz of water once or twice daily as first-line therapy for acute constipation, and add bisacodyl as rescue therapy if no response occurs within 24-48 hours. 1
Initial Assessment
Before initiating treatment, you must rule out:
- Mechanical bowel obstruction through clinical evaluation 1
- Fecal impaction via digital rectal examination if the rectum is accessible 2
- Red flag features including severe abdominal pain, blood in stool, unintentional weight loss, or new-onset constipation in older adults 2
First-Line Pharmacological Treatment
Polyethylene glycol (PEG) is the preferred initial agent based on strong evidence for efficacy, tolerability, and safety in acute settings 2, 1:
- Dosing: 17g (one capful) mixed in 8 oz water, administered 1-2 times daily 2, 1
- Expected side effects: Abdominal distension, loose stool, flatulence, and nausea (generally mild) 1
- Mechanism: Osmotic laxative that increases water content in stool 2
Alternative First-Line Options
Stimulant laxatives (senna, bisacodyl, sodium picosulfate) are equally appropriate for acute constipation 2, 1:
- Bisacodyl: 2-3 tablets orally or one suppository daily 2, 1
- Senna: 2 tablets every morning (maximum 8-12 tablets per day) 2
- These agents are strongly recommended for short-term use (≤4 weeks) or as rescue therapy 1
Rescue Therapy Algorithm
If no bowel movement within 24-48 hours of starting PEG:
- Add bisacodyl 2-3 tablets orally or one suppository 2, 1
- Consider rectal interventions if digital rectal exam identifies retained stool 2
For fecal impaction identified on examination:
- Suppositories or enemas are first-line therapy when digital rectal exam confirms a full rectum 2
- Manual disimpaction may be necessary (digital fragmentation and extraction), followed by maintenance therapy 2
- Isotonic saline enemas are preferred over sodium phosphate enemas due to better safety profile 2
Second-Line Options for Persistent Constipation
If constipation persists after 48-72 hours despite PEG and bisacodyl:
Supportive Measures
Concurrent lifestyle modifications enhance pharmacological efficacy:
- Increase fluid intake to at least 1.5-2 liters daily, particularly when using osmotic laxatives 2
- Encourage physical activity if feasible 2
- Optimize toileting habits: Attempt defecation 30 minutes after meals, limit straining to <5 minutes 2
What NOT to Do
Avoid these interventions in acute constipation:
- Bulk-forming laxatives (psyllium, methylcellulose) are insufficient for acute constipation and may worsen symptoms without adequate fluid intake 2, 1
- Liquid paraffin in patients with swallowing difficulties (aspiration risk) 2
- Enemas are contraindicated in neutropenia, thrombocytopenia, recent pelvic surgery, severe colitis, or undiagnosed abdominal pain 2
Reassessment Points
If no response after 3-5 days of combined therapy:
- Reassess for obstruction through physical examination and consider imaging if clinical suspicion exists 2
- Check for impaction via digital rectal examination 2
- Consider adding a prokinetic agent such as metoclopramide 10-20 mg three times daily 2
Transition to Maintenance
Once bowel function normalizes:
- Continue PEG at reduced frequency (every other day or as needed) for prevention 1
- Goal: One non-forced bowel movement every 1-2 days 2, 1
- Maintain lifestyle modifications including adequate hydration and dietary fiber 2
Common Pitfalls to Avoid
Do not perform routine abdominal x-rays for straightforward acute constipation without red flags, as clinical history is sufficient for diagnosis 3. Digital rectal examination has diagnostic and therapeutic value when impaction is suspected but should not be routine in all cases 3. Fiber supplementation is inappropriate for acute constipation management as it requires time to work and adequate baseline fiber intake 1.