How should acute constipation be managed in an otherwise healthy adult without bowel obstruction, perforation, inflammatory bowel disease flare, severe electrolyte abnormalities, or recent abdominal surgery?

Acute Constipation Treatment in Healthy Adults

For acute constipation in an otherwise healthy adult, start with oral polyethylene glycol (PEG) 17g daily mixed in 8 ounces of liquid, and if no response within 24-48 hours, add a stimulant laxative such as senna or bisacodyl. 1

Initial Pharmacologic Management

First-Line: Osmotic Laxatives

• Polyethylene glycol (PEG) is the preferred first-line agent because it works by sequestering fluid in the bowel through osmotic action, has minimal systemic absorption, and offers an excellent safety profile 1
• Dose PEG at 17g once daily mixed in 8 ounces of liquid, titrating based on response to achieve at least one spontaneous bowel movement every 1-2 days 1
• Alternative osmotic agents include lactulose or magnesium salts, though magnesium must be avoided in any degree of renal impairment due to hypermagnesemia risk 2, 1

Second-Line: Add Stimulant Laxatives

• If PEG alone fails after 24-48 hours, add a stimulant laxative such as senna or bisacodyl, which enhance intestinal motility and peristalsis 2, 1
• Bisacodyl is available as both oral tablets and rectal suppositories, allowing flexible administration 1
• Sodium picosulfate is another stimulant option 2

Agents to Avoid

• Do not prescribe docusate (stool softeners) as multiple trials demonstrate lack of clinical benefit 1
• Avoid bulk-forming laxatives like psyllium in acute constipation, especially if the patient has limited mobility or inadequate fluid intake, as they require at least 8 ounces of water per dose and carry obstruction risk 1

Non-Pharmacologic Measures

Supportive Care

• Ensure adequate fluid intake guided by thirst; drinks containing glucose (lemonades, fruit juices) or electrolyte-rich soups are recommended 2
• Maintain food intake guided by appetite with small, light meals; avoid fatty, heavy, spicy foods and caffeine 2
• Increase physical activity and mobility within patient limits, as regular activity modestly improves constipation symptoms 1

Toileting Optimization

• Educate patients to attempt defecation at least twice daily, preferably 30 minutes after meals when the gastrocolic reflex is strongest 3
• Ensure privacy, comfort, and proper positioning; a small footstool may help patients exert pressure more easily by assisting gravity 2
• Instruct patients to strain no more than 5 minutes per attempt 2

When to Escalate Treatment

Rectal Interventions for Severe Cases

• If digital rectal examination identifies a full rectum or fecal impaction, suppositories and enemas become first-line therapy 2
• For distal fecal impaction, perform digital fragmentation and extraction after administering appropriate analgesia and/or anxiolytic, followed by water or oil retention enema 3
• Mineral oil enemas (120 mL) are the safest small-volume option as they lubricate and soften stool without causing electrolyte disturbances 3, 4
• Glycerin suppositories provide mild rectal stimulation and typically produce a bowel movement within 15-60 minutes 3, 4

Contraindications for Enemas

• Never use enemas in patients with neutropenia, thrombocytopenia, paralytic ileus, intestinal obstruction, recent colorectal or gynecological surgery, recent anal or rectal trauma, severe colitis, toxic megacolon, or undiagnosed abdominal pain 2, 3, 4

Treatment Algorithm

1. Start with PEG 17g daily mixed in adequate fluid, ensuring patient maintains hydration and mobility 1
2. If no response in 24-48 hours, add senna or bisacodyl while continuing PEG 1
3. If rectal examination reveals impaction, use mineral oil enema or glycerin suppository in addition to oral laxatives 3, 4
4. Reassess after 3 days of optimized therapy; if no adequate response, consider underlying causes or refer for further evaluation 1

Common Pitfalls to Avoid

• Do not prescribe docusate based on tradition—it has no proven efficacy in multiple trials 1
• Do not use magnesium-containing laxatives without confirming normal renal function, as even mild renal impairment can lead to dangerous hypermagnesemia 1
• Do not use bulk-forming agents in acute constipation, particularly in patients with limited mobility or opioid use, as they may worsen symptoms and cause obstruction 1
• Do not delay adding a stimulant laxative if osmotic therapy alone is insufficient after 24-48 hours 1
• Do not use sodium phosphate enemas in patients with renal dysfunction or cardiac disease due to risks of electrolyte disturbances, fluid shifts, and cardiac arrhythmias 3