What is a Peglec enema (polyethylene glycol 3350‑electrolyte solution) and how does it work?

What is a Peglec Enema and How Does It Work?

A "Peglec enema" refers to rectal administration of polyethylene glycol 3350 with electrolyte solution (PEG 3350-E), which works by osmotically retaining water in the colon to soften impacted stool and facilitate evacuation—this approach is primarily used for disimpaction in severe constipation, particularly in pediatric populations.

Mechanism of Action

PEG 3350 is a long-chain polymer of ethylene oxide that exerts a purely physical osmotic effect by binding water molecules in the intestinal lumen, thereby retaining water in the stool and softening its consistency. 1 Unlike stimulant laxatives, PEG does not stimulate colonic smooth-muscle contractions or activate ion channels; its laxative action is entirely through water retention. 1

When administered rectally as an enema, the PEG 3350-electrolyte solution delivers this osmotic effect directly to the distal colon and rectum, making it particularly effective for fecal impaction that has not responded to oral therapy alone. 2

Clinical Applications

Disimpaction in Pediatric Constipation

The most robust evidence for PEG enema therapy comes from pediatric disimpaction protocols, where combined oral and enema therapy using PEG 3350-electrolyte solution has demonstrated superior efficacy and safety compared to conventional oral monotherapy. 2

• The recommended enema dose is 15-25 mL/kg per administration (containing PEG 3350 0.975-1.625 g/kg), administered 1-2 times daily. 2
• This approach increased defecation frequency from 2.2 times per week to once daily (1.1 times per day) and reduced abdominal pain complaints from 53.6% to 14.3% of patients. 2
• Combined oral (50-70 mL/kg/day of PEG 3350-E solution) and enema therapy showed excellent therapeutic efficacy with only mild adverse effects. 2

Fecal Impaction in Adults

For adults with fecal impaction in the ascending colon, high-dose PEG therapy is recommended at 4 liters divided over 2 days (2 liters per day), preferably in divided doses to improve tolerability. 3 While this guideline refers to oral administration, the principle of high-volume PEG therapy for impaction applies to rectal administration when oral intake is not feasible or has failed.

Safety Profile

Electrolyte and Metabolic Safety

PEG 3350 with electrolytes is isotonic and iso-osmolar, making it the safest option for patients with comorbidities, particularly those at risk for electrolyte disturbances. 3

• In pediatric studies of combined oral and enema PEG therapy, electrolytes and osmolality measured before and after disimpaction showed no abnormalities. 2
• Long-term studies (up to 52 weeks) of oral PEG therapy revealed no clinically significant changes in electrolytes, calcium, glucose, BUN, creatinine, or serum osmolality. 1
• Urinary excretion studies demonstrate minimal systemic absorption, with only 0.06-0.09% of the PEG load recovered in urine, indicating negligible risk of toxicity. 4

Common Adverse Effects

• Mild gastrointestinal symptoms including abdominal distension, bloating, cramping, flatulence, and nausea are the most common adverse effects, typically mild to moderate in severity. 1
• These effects are consistent with expected laxative action and rarely lead to treatment discontinuation. 1

Practical Considerations

When to Use Enema Therapy

Add rectal PEG therapy when oral PEG has failed to produce a bowel movement after 3-4 days of optimal dosing with adequate hydration. 5

• Rule out bowel obstruction or paralytic ileus before initiating any PEG therapy (oral or rectal). 5
• Check for fecal impaction, which may require manual disimpaction or enema therapy first before resuming oral maintenance therapy. 5

Advantages Over Other Preparations

• PEG-electrolyte solutions are preferred over hyperosmotic preparations (sodium phosphate, magnesium-containing solutions) because they minimize electrolyte imbalances, especially critical in patients with renal disease, heart failure, or other comorbidities. 3
• The isotonic formulation makes PEG-E safer than tap water enemas or other hypotonic/hypertonic solutions that can cause fluid and electrolyte shifts. 3

Common Clinical Pitfalls

• Insufficient fluid volume: When using oral PEG, inadequate liquid volume is a common cause of treatment failure; patients must maintain adequate daily fluid intake beyond just the mixing liquid. 1, 5
• Premature discontinuation: Assuming treatment failure without first optimizing dose and ensuring compliance can lead to unnecessary escalation or alternative therapies. 5
• Delaying rectal intervention: Waiting beyond 3-4 days without a bowel movement increases the risk of worsening fecal impaction. 5
• Using in contraindicated populations: Avoid in patients with known or suspected bowel obstruction, paralytic ileus, or toxic megacolon. 5