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Polyethylene Glycol 3350

Generic name: polyethylene glycol 3350 systemic

Brand names: GlycoLax, MiraLAX, GaviLAX, ClearLax, SunMark ClearLax, PEG3350, Purelax, HealthyLax, Gialax

Dosage Forms

Excipient information presented when available (limited, particularly for generics); consult specific product labeling. [DSC] = Discontinued product

Kit, Oral:

Gialax: [contains aspartame, polyethylene glycol (interact starch), tartrazine (fd&c yellow #5)]

Packet, Oral:

HealthyLax: (1 ea, 14 ea) [contains polyethylene glycol (interact starch)]

MiraLax: (1 ea [DSC], 10 ea, 12 ea [DSC], 24 ea) [contains polyethylene glycol (interact starch)]

Generic: (1 ea, 14 ea, 30 ea, 100 ea)

Powder, Oral:

GaviLAX: 17 g/dose (238 g, 510 g) [contains polyethylene glycol (interact starch)]

GlycoLax: 17 g/dose (119 g, 255 g, 527 g) [contains polyethylene glycol (interact starch)]

MiraLax: 17 g/dose (1 ea, 119 g, 238 g, 510 g, 765 g) [contains polyethylene glycol (interact starch)]

PEGyLAX: 17 g/dose (527 g [DSC]) [contains polyethylene glycol (interact starch)]

Generic: 17 g/dose (119 g, 238 g, 255 g, 510 g, 527 g, 850 g)


Mechanism of Action

An osmotic agent, polyethylene glycol 3350 causes water retention in the stool; increases stool frequency.



Minimal (<0.28%; Pelham, 2008)


Feces (93%); urine (0.2%) (Pelham, 2008)

Onset of Action

Oral: 24 to 96 hours

Use: Labeled Indications

Constipation, occasional: Treatment of occasional constipation

Use: Off Label

Bowel preparation before colonoscopyyes

Based on the Consensus Document on Bowel Preparation Before Colonoscopy from The American Society of Colon and Rectal Surgeons (ASCRS), The American Society for Gastrointestinal and Endoscopy (ASGE), and The Society of American Gastrointestinal and Endoscopic Surgeons (SAGES), polyethylene glycol 3350 in combination with bisacodyl delayed-release tablets or magnesium citrate is effective and recommended for bowel preparation before colonoscopy Wexner 2006.


Hypersensitivity to polyethylene glycol or any component of the formulation; known or suspected bowel obstruction

OTC labeling: When used for self-medication, do not use if you have renal disease unless advised by a health care provider

Canadian labeling: Additional contraindications (not in US labeling): Relaxa: Use in children <18 years of age unless advised by a physician

Dosage and Administration

Dosing: Adult

Bowel preparation before colonoscopy (off-label use): Oral: 17 g (~1 heaping tablespoon) in 240 mL (8 ounces) of clear liquid every 10 minutes until 2,000 mL of volume are consumed (start within 6 hours after administering bisacodyl delayed-release tablets or magnesium citrate) (ASCRS/ASGE/SAGES [Wexner 2006])

Constipation, occasional: Oral: 17 g (~1 heaping tablespoon) dissolved in 120 to 240 mL (4 to 8 ounces) of beverage, once daily; do not use for >1 to 2 weeks (product specific) unless directed by health care provider. In a clinical trial, 34 g once daily was shown to be effective, but with increased adverse effects (DiPalma 1999).

Dosing: Geriatric

Refer to adult dosing.

Dosing: Pediatric

Bowel preparation: Limited data available: Children >2 years and Adolescents: Oral: 1.5 g/kg/day for 4 days; maximum daily dose: 100 g/day (Pashankar 2004)

Constipation: Limited data available: Infants, Children, and Adolescents: Oral: 0.2 to 0.8 g/kg/day (NASPGHAN [Tabbers] 2014); higher initial dose of 1 g/kg have been suggested ( Loening-Buck 2004; Pashankar 2001); maximum daily dose: 17 g/day. Note: Dosage should be individualized to achieved desired effect, infants and young children may require higher doses than school aged children (Loening-Buck 2004; Pashankar 2001)

Fecal impaction, slow disimpaction: Limited data available: Children and Adolescents: Oral: 1 to 1.5 g/kg daily for 3 to 6 consecutive days (NASPGHAN [Tabbers] 2014; Youssef 2002); maximum daily dose: 100 g/day (Youssef 2002); following disimpaction maintenance dose of 0.4 g/kg daily should be continued for ≥ 2 months (NASPGHAN [Tabbers] 2014)


Dissolve powder completely in 120 to 240 mL (4 to 8 ounces) of water, juice, soda, coffee, or tea.



Constipation, occasional: Stir powder in 120 to 240 mL (4 to 8 ounces) of water, juice, soda, coffee, or tea until dissolved and administer immediately.

Bowel preparation for colonoscopy (off-label use): Administer bisacodyl delayed-release tablets or magnesium citrate prior to polyethylene glycol administration. After bowel movement (or up to 6 hours later if no bowel movement), stir powder in 240 mL (8 ounces) of clear liquid until dissolved and administer immediately. Dose is repeated every 10 minutes until 2,000 mL of volume is consumed.


Store at 20°C to 25°C (68°F to 77°F); excursions are permitted between 15°C to 30°C (59°F to 86°F).

Drug Interactions

Dichlorphenamide: Laxatives may enhance the hypokalemic effect of Dichlorphenamide. Monitor therapy

Digoxin: Polyethylene Glycol 3350 may decrease the serum concentration of Digoxin. Monitor therapy

Adverse Reactions

>10%: Gastrointestinal: Gastrointestinal signs and symptoms (32%; Di Palma 2007), diarrhea (11%; DiPalma 2006)

1% to 10%: Gastrointestinal: Flatulence (7%; DiPalma 2006), nausea (6%; DiPalma 2006), abdominal pain (5%; DiPalma 2006), loose stools (4%; DiPalma 2006), abdominal distention (3%; DiPalma 2006)

Frequency not defined.

Gastrointestinal: Dyspepsia (Di Palma 2007), eructation (Di Palma 2007), stomach discomfort (Di Palma 2007)

Hematologic & oncologic: Rectal hemorrhage (Di Palma 2007)


Concerns related to adverse effects:

  • Electrolyte imbalance: Prolonged, frequent, or excessive use may lead to electrolyte imbalance.
  • Hypersensitivity: Do not use if you are hypersensitive to polyethylene glycol. If an allergic reaction develops (eg, rash, swelling, difficulty breathing), discontinue use immediately and seek medical care.

Disease-related concern:

  • Bowel obstruction: Evaluate patients with symptoms of bowel obstruction, appendicitis, or inflamed bowel (nausea, vomiting, abdominal pain or distension) prior to use; use is contraindicated in patients with known or suspected bowel obstruction.
  • Renal impairment: Use with caution in patients with renal impairment. Do not use in renal impairment unless under supervision of a health care professional.

Other warnings/precautions:

  • Administration: If severe diarrhea occurs, discontinue use. When used for bowel preparation for colonoscopy (off-label use), oral medications should not be administered within 1 hour of start of therapy.
  • Duration of therapy: Do not use for longer than 1 to 2 weeks (product specific); 2 to 4 days may be required to produce bowel movement.
  • OTC labeling: When used for self-medication, patients should consult health care provider prior to use if they have nausea, vomiting, or abdominal pain, irritable bowel syndrome, or a sudden change in bowel habits for >2 weeks. Patients should be instructed to discontinue use and consult health care provider if they have severe diarrhea, rectal bleeding, if abdominal pain, bloating, cramping, or nausea gets worse, or if need to use for >1 week.


Pregnancy Considerations

Polyethylene glycol (PEG) has minimal systemic absorption and would be unlikely to cause fetal malformations. However, until additional information is available, use to treat constipation in pregnancy should be avoided unless other preferred methods are inadequate (Mahadevan 2006). Use as a bowel preparation prior to colonoscopy in pregnant women may be considered (Wexner 2006).

Patient Education

What is this drug used for?

  • It is used to treat constipation.

Frequently reported side effects of this drug

  • Abdominal pain
  • Abdominal cramps
  • Bloating
  • Nausea
  • Passing gas

Other side effects of this drug: Talk with your doctor right away if you have any of these signs of:

  • Severe dizziness
  • Passing out
  • Diarrhea
  • Rectal bleeding
  • Rectal pain
  • Signs of a significant reaction like wheezing; chest tightness; fever; itching; bad cough; blue skin color; seizures; or swelling of face, lips, tongue, or throat.

Note: This is not a comprehensive list of all side effects. Talk to your doctor if you have questions.

Consumer Information Use and Disclaimer: This information should not be used to decide whether or not to take this medicine or any other medicine. Only the healthcare provider has the knowledge and training to decide which medicines are right for a specific patient. This information does not endorse any medicine as safe, effective, or approved for treating any patient or health condition. This is only a brief summary of general information about this medicine. It does NOT include all information about the possible uses, directions, warnings, precautions, interactions, adverse effects, or risks that may apply to this medicine. This information is not specific medical advice and does not replace information you receive from the healthcare provider. You must talk with the healthcare provider for complete information about the risks and benefits of using this medicine.

Source: Wolters Kluwer Health. Last updated January 24, 2020.