How Laxopeg (Polyethylene Glycol) Works
Laxopeg works as an osmotic laxative by retaining water in the stool through its long-chain polymer structure, which softens stool and increases bowel movement frequency without causing significant electrolyte disturbances. 1, 2
Mechanism of Action
Polyethylene glycol (PEG) is a long-chain polymer of ethylene oxide that functions purely through osmotic effects. 1 The medication is absorbed in only trace amounts from the gastrointestinal tract, meaning it remains in the intestinal lumen where it exerts its therapeutic effect. 3
PEG creates an osmotic gradient that draws water into the intestinal lumen and retains it within the stool mass. 2, 4 This water retention directly softens hard stool and increases its volume, making passage easier and more comfortable.
The molecular structure (HO(C2H4O)nH, where n represents the average number of oxyethylene groups) allows PEG to be freely soluble in water while remaining non-absorbable. 2 This property is critical—because PEG stays in the bowel rather than being absorbed systemically, it causes virtually no net electrolyte disturbance, unlike other osmotic agents such as magnesium or phosphate salts. 1
The efficacy of PEG is dose-dependent, with standard dosing at 17g daily for chronic constipation management. 1, 4 Higher doses (68g) can provide relief within 24 hours for acute constipation. 5
Clinical Effects and Timeline
Your first bowel movement typically occurs within 2-4 days of starting therapy, though individual response varies. 2 The medication achieves its best results when used between 1-2 weeks. 2
PEG increases both complete spontaneous bowel movements (CSBMs) by approximately 2.90 per week and spontaneous bowel movements (SBMs) by 2.30 per week compared to placebo. 1
Response to PEG has been shown to be durable over 6 months, making it suitable for long-term management of chronic constipation. 1
Safety Profile
PEG is remarkably safe with minimal systemic effects because it is not absorbed. 3, 4 Common side effects are mild and related to its mechanism:
- Bloating, abdominal distension, flatulence, and nausea may occur but are generally well-tolerated. 1
- Diarrhea can develop if the dose is too high, but this resolves with dose adjustment. 1
- No clinically significant changes occur in electrolytes, calcium, glucose, BUN, creatinine, or serum osmolality, even with higher doses. 5
Clinical Context
PEG is recommended as a first-line osmotic laxative by major gastroenterology guidelines, preferred over lactulose and other osmotic agents. 1 It is particularly valuable because:
- It can be used safely long-term without predetermined stop dates. 1
- It works for both chronic constipation and opioid-induced constipation. 1
- Unlike magnesium-based laxatives, PEG does not require dose adjustment in renal impairment since it causes no electrolyte disturbances. 1
A critical pitfall to avoid: PEG should not be used if bowel obstruction is suspected, as symptoms like nausea, vomiting, or abdominal distention may indicate mechanical blockage rather than functional constipation. 2