Miralax is Polyethylene Glycol 3350
Yes, Miralax is polyethylene glycol 3350, an osmotic laxative available over the counter for the treatment of constipation. 1
Composition and Mechanism
Polyethylene glycol (PEG) 3350 is the active ingredient in Miralax, with each standard dose containing 17 grams of PEG 3350 1. It works as an osmotic laxative by:
- Increasing water content in the colon
- Softening stool
- Promoting more frequent bowel movements
- Being poorly absorbed, with minimal systemic effects
Clinical Uses
PEG 3350 (Miralax) is primarily used for:
- Treatment of occasional constipation - FDA-approved for short-term use 1
- Management of chronic constipation - Supported by clinical evidence for longer-term use 2, 3
- Bowel preparation for colonoscopy - Although not FDA-approved for this purpose, it is widely used in "split-dose" regimens 4
- Treatment of constipation in irritable bowel syndrome with constipation (IBS-C) - Recommended by guidelines 4
Efficacy and Safety
PEG 3350 has demonstrated strong efficacy and safety profiles:
- Efficacy: Clinical trials show successful treatment in 52-61% of patients with chronic constipation versus 11-22% with placebo 3
- Long-term safety: Studies demonstrate safety for up to 12 months of continuous use with no evidence of tachyphylaxis (decreased response over time) 2
- Elderly patients: Similar efficacy and safety profiles in elderly populations 2, 3
- Rapid onset: Higher doses (68g) can provide relief within 24 hours for acute constipation 5
Important Clinical Considerations
Advantages of PEG 3350:
- Minimal systemic absorption
- No clinically significant changes in electrolytes with long-term use 2
- Better tolerability compared to other laxatives 6
- Can be used in patients with renal insufficiency, congestive heart failure, and advanced liver disease due to its iso-osmotic properties 4
Side Effects:
- Most common: diarrhea, loose stools, flatulence, and nausea 2, 3
- Generally mild to moderate in severity
- No significant changes in hematology or blood chemistry, including electrolytes 2
Contraindications:
Special Populations
Children:
- Polyethylene glycol is recommended as a first-line treatment for constipation in children 7
- Standard dose is 17g daily mixed in 4-8 ounces of liquid 7
Elderly:
- Safe and effective in elderly patients with similar efficacy to younger adults 2, 3
- No dose adjustment required based on age
Formulations and Dosing
- Standard dose: 17g once daily mixed in 4-8 ounces of liquid 1, 8
- Duration: FDA-approved for short-term use, but clinical evidence supports safety for up to 12 months 2
- Bowel preparation: When used for colonoscopy preparation, typically administered in split-dose regimens, though this is not an FDA-approved indication 4
Important Note on Off-Label Use
The US Multi-Society Task Force on Colorectal Cancer notes that using over-the-counter PEG-3350 (Miralax) mixed with sports drinks for bowel preparation before colonoscopy, while widely practiced, is not FDA-approved for this purpose 4.