What is polyethylene glycol 3350 used for? A comprehensive guide to its applications

October 9, 2025 •

3 min read

According to the American College of Gastroenterology, approximately 16% of adults suffer from symptoms of constipation. Polyethylene glycol 3350 is a common and effective medication used to provide relief from this condition and as a bowel cleanser for medical procedures.

Quick Summary

Polyethylene glycol 3350 is an osmotic laxative that works by drawing water into the colon to soften stool. It is primarily used to relieve occasional constipation and for complete bowel clearance before colonoscopies. Available over-the-counter, it is generally well-tolerated and effective for short-term relief.

Key Points

Osmotic Laxative: Polyethylene glycol 3350 works by drawing water into the colon to soften stool and ease bowel movements.
Treats Constipation: Its primary use is for the short-term treatment of occasional constipation in adults and children (under medical guidance).
Bowel Preparation: It is also used in higher doses as part of the bowel cleansing process before medical procedures like colonoscopies.
Gentle and Safe for Long-Term Use: Compared to stimulant laxatives, it is generally gentler on the system and can be used long-term for chronic constipation under a doctor's supervision.
Available Over-the-Counter: The medication is widely available without a prescription under brand names like MiraLAX and various generics.

The Mechanism Behind Polyethylene Glycol 3350

Polyethylene glycol 3350, or PEG 3350, is a form of an osmotic laxative that draws water into the intestinal tract. Its active ingredient is a non-digestible and non-absorbable polymer that passes through the body largely intact. As it moves through the gut, it attracts and holds water molecules via hydrogen bonds. This mechanism increases the fluid content in the stool and adds bulk, making the stool softer and easier to pass. Unlike some other laxatives, it works gently and typically does not cause the muscle contractions associated with stimulant laxatives. The result is a bowel movement that feels more natural, usually occurring within one to three days of the first dose.

Primary Application: Treating Occasional Constipation

This medication is a go-to choice for managing occasional constipation in adults and children (when directed by a doctor). It is available over-the-counter as an unflavored powder, often sold under the brand name MiraLAX or its generic versions.

To use for occasional constipation:

Mix one dose (17 grams or one heaping tablespoon) of the powder into 4 to 8 ounces of a beverage, such as water, juice, or tea.
Stir until the powder is completely dissolved.
Drink the solution immediately after mixing.
Take once daily for up to seven days, unless otherwise directed by a healthcare provider.

Secondary Application: Bowel Preparation for Medical Procedures

In higher doses and sometimes combined with electrolytes, PEG 3350 is used to completely cleanse the bowel in preparation for a colonoscopy or other intestinal procedures. During this process, patients typically follow a strict schedule for drinking the solution over a period of time, along with a clear liquid diet. The volume of solution and timing are critical for a successful procedure, so patients must follow their doctor's instructions precisely.

Use in Pediatric Constipation

For children experiencing chronic constipation, PEG 3350 is often recommended as a first-line treatment. It is considered safe and effective for long-term use in children under a physician's guidance. Dosage for pediatric patients is determined by a doctor based on the child's age and weight.

Potential Side Effects and Safety Considerations

While PEG 3350 is generally well-tolerated, some individuals may experience side effects. Common adverse effects include:

Nausea
Bloating
Gas (flatulence)
Stomach cramping
Diarrhea

Serious side effects are rare, but include severe allergic reactions (hives, swelling, difficulty breathing) and severe or bloody diarrhea. Discontinue use and contact a doctor immediately if these occur. Long-term or excessive use can lead to dependency and electrolyte imbalances, so it is important to follow dosage instructions and not use for more than seven days for occasional constipation without consulting a healthcare professional.

PEG 3350 vs. Other Laxative Types

To better understand how PEG 3350 compares to other common laxatives, consider this table:


Feature	PEG 3350 (Osmotic)	Bulk-Forming Laxatives (e.g., Psyllium)	Stimulant Laxatives (e.g., Bisacodyl)
Mechanism of Action	Draws water into the colon to soften stool and increase bulk.	Absorbs water to form a gel-like mass, increasing stool bulk.	Irritates the intestinal lining, causing muscle contractions.
Speed of Action	Works gradually, typically within 1-3 days.	Slower-acting, also takes 1-3 days to be fully effective.	Fastest-acting, works within hours (oral) or minutes (suppository).
Primary Use	Occasional constipation, chronic constipation (long-term), and bowel prep.	Long-term use for chronic constipation, and increasing fiber intake.	Short-term relief for severe constipation; not for long-term use due to dependency risk.
Common Side Effects	Bloating, gas, nausea, cramping.	Bloating, gas, fullness, cramping (can be more pronounced).	Abdominal cramping, stomach discomfort, diarrhea.

Conclusion

Polyethylene glycol 3350 is a versatile and widely-used osmotic laxative known for its effectiveness in treating occasional constipation and preparing the bowel for procedures like colonoscopies. Its gentle, non-stimulant mechanism of action makes it a suitable option for both adults and children, often with fewer side effects like gas and bloating compared to some other laxatives. Proper usage, adhering to recommended dosages and duration, is key to its safe and effective application. For personalized advice, especially for chronic conditions or use in children, consulting a healthcare professional is always the best approach. More information on its use can be found at the MedlinePlus Drug Information page.

Frequently Asked Questions

Polyethylene glycol 3350 is an osmotic laxative that works gently by drawing water into the colon. A stimulant laxative, like bisacodyl, irritates the intestinal lining to force a muscle contraction and is faster-acting, but can be harsher and carries a higher risk of dependency with long-term use.

For occasional constipation, polyethylene glycol 3350 typically takes between one and three days to produce a bowel movement. For bowel preparation, the effect is much quicker due to the higher, more concentrated dose.

For occasional constipation, it is not recommended to use for more than seven days in a row without consulting a doctor. However, a physician may prescribe it for daily, long-term use in cases of chronic constipation, including in children.

You can mix the unflavored powder with 4 to 8 ounces of any beverage, including water, juice, soda, coffee, or tea. It is recommended to stir until completely dissolved before drinking.

Yes, PEG 3350 is considered safe and effective for treating chronic constipation in children, often with a high rate of acceptance. However, it should only be administered to children under a doctor's guidance, who will determine the appropriate dosage.

Mild side effects like bloating and gas are common and may decrease with continued use. Ensuring adequate fluid intake and adhering to the recommended dosage can help. If symptoms persist or worsen, consult your doctor.

MiraLAX is a brand-name product that contains the active ingredient polyethylene glycol 3350 (PEG 3350). The generic versions of the medication contain the same active ingredient and work in the same way, often at a lower cost.