An osmotic laxative composed of polyethylene glycol 3350, used for the treatment of occasional constipation and chronic idiopathic constipation. PEG 3350 is also used in higher doses for bowel preparation before colonoscopy. It is well-tolerated and does not cause electrolyte imbalances at standard doses.
Evidence rating strong. Most-documented uses: relief of occasional constipation, treatment of chronic idiopathic constipation, bowel preparation for colonoscopy (high-dose formulations). 10 sources indexed (2009–2020), with 2 interaction records on file.
The science
How it works, mechanistically.
Core mechanism
Acts as an osmotic agent in the intestinal lumen, retaining water through hydrogen bonding. The increased water content in the stool softens it and increases stool volume, stimulating peristalsis. PEG 3350 is not absorbed or metabolized, and it does not stimulate the colonic mucosa directly.
Class
Osmotic Laxative
Dosing
Dosing & protocol.
Common range
17 g (1 capful) dissolved in 8 oz of liquid once daily for up to 7 days (as prescribed by your physician)
Recommended form
Powder dissolved in water or other beverage
Dissolve powder completely in 4–8 oz of water, juice, or other beverage; can be taken at any time of day
High-volume polyethylene glycol electrolyte lavage used for whole bowel irrigation can interfere with activated charcoal's toxin-binding role if the two are mixed or coadministered improperly. An in vitro study found PEG lavage solution caused desorption of theophylline from activated charcoal, and toxicology position guidance discusses sequencing charcoal and whole bowel irrigation separately. This concern applies to poisoning management or lavage-level PEG use, not ordinary once-daily constipation dosing.
Recommendation: Do not self-combine activated charcoal with high-dose PEG bowel prep or whole-bowel-irrigation regimens. For suspected poisoning, call poison control or emergency services; charcoal timing, PEG lavage, airway safety, and the substance ingested need clinician direction. Avoid taking activated charcoal close to routine oral medicines because it can reduce their absorption.
Polyethylene glycol bowel-preparation products are sometimes formulated with gram-dose ascorbic acid to improve cleansing with a lower PEG volume. Randomized trials support PEG plus ascorbate regimens for colonoscopy preparation, but this evidence applies to medically directed bowel-prep dosing rather than routine daily vitamin C supplementation with OTC PEG for constipation.
Recommendation: Use PEG plus high-dose vitamin C only when it is part of a prescribed or procedure-directed bowel-prep regimen. Do not add large vitamin C doses to PEG laxative use on your own, especially if you have kidney disease, a history of oxalate kidney stones, dehydration risk, or electrolyte problems. Follow the prep instructions and hydration plan exactly.
Afkhami Ardekani M, Ghaffari H. Optimization of prostate brachytherapy techniques with polyethylene glycol-based hydrogel spacers: A systematic review. Brachytherapy. 2020
Rachel H, Griffith AF, Teague WJ et al.. Polyethylene Glycol Dosing for Constipation in Children Younger Than 24 Months: A Systematic Review. Journal of pediatric gastroenterology and nutrition. 2020
Jin Z, Lu Y, Zhou Y et al.. Systematic review and meta-analysis: sodium picosulfate/magnesium citrate vs. polyethylene glycol for colonoscopy preparation. European journal of clinical pharmacology. 2016
Siddique S, Lopez KT, Hinds AM et al.. Miralax with gatorade for bowel preparation: a meta-analysis of randomized controlled trials. The American journal of gastroenterology. 2014
Belsey JD, Geraint M, Dixon TA. Systematic review and meta analysis: polyethylene glycol in adults with non-organic constipation. International journal of clinical practice. 2010
Candy D, Belsey J. Macrogol (polyethylene glycol) laxatives in children with functional constipation and faecal impaction: a systematic review. Archives of disease in childhood. 2009
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