What is the proper dosing of Polyethylene Glycol (PEG) (Miralax) for the treatment of chronic constipation?

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From the Guidelines

For chronic constipation, MiraLAX (polyethylene glycol 3350) should be prescribed at a standard dose of 17 grams (one capful or one heaping tablespoon) dissolved in 8 ounces of water, juice, or other beverage once daily, as recommended by the most recent guidelines 1.

Key Considerations

  • The medication works by drawing water into the colon to soften stool and increase bowel movements, making it an effective osmotic laxative for chronic constipation management 1.
  • Patients should take this consistently at the same time each day, typically in the morning, and adjust the dose based on response, with some needing only 8.5 grams (half a capful) daily and others up to 34 grams (two capfuls) daily 1.
  • MiraLAX typically produces a bowel movement within 1-3 days of starting treatment and is gentle and non-habit forming, as it works osmotically rather than stimulating the bowel 1.
  • Patients should also be advised to increase fluid intake, physical activity, and dietary fiber while using MiraLAX to enhance its effectiveness and overall bowel health 1.

Monitoring and Follow-Up

  • If symptoms persist beyond two weeks of daily use or worsen, patients should consult their healthcare provider for further evaluation and potential adjustment of the treatment plan 1.
  • The side effect profile of PEG is generally mild, with bloating, flatulence, and diarrhea being common but manageable, making it a safe long-term option for many patients with chronic constipation 1.

From the FDA Drug Label

ACTIVE INGREDIENT (IN EACH DOSE) (Bottle Only) Polyethylene Glycol 3350,17 g (cap filled to line) (Packet Only) Polyethylene Glycol 3350,17 g The FDA drug label does not answer the question.

From the Research

Prescribing Miralax for Chronic Constipation

  • Miralax, also known as polyethylene glycol (PEG), is an osmotic laxative that can be used to treat chronic constipation 2, 3.
  • The evidence suggests that PEG is a first-line treatment option for chronic constipation, with good evidence (grade A recommendation) supporting its use 2, 3.
  • When prescribing Miralax, it is essential to follow the recommended dosage and administration instructions to minimize adverse effects such as abdominal pain, cramping, bloating, diarrhea, and nausea 2, 3.

Treatment Recommendations

  • The treatment of chronic constipation typically involves a step-wise approach, starting with lifestyle modifications such as increased dietary fiber, fluid, and exercise 4, 5.
  • If lifestyle modifications are insufficient, osmotic or stimulant laxatives like Miralax can be used as first-line treatments 4, 5.
  • Other treatment options, such as prokinetics and secretagogues, may be considered for patients who do not respond to basic treatment 4, 5.

Safety and Efficacy

  • Miralax has been shown to be generally well-tolerated, with common adverse effects being abdominal pain, cramping, bloating, diarrhea, and nausea 2, 3.
  • The evidence suggests that Miralax is effective in treating chronic constipation, with good evidence (grade A recommendation) supporting its use 2, 3.
  • However, it is crucial to monitor patients for potential adverse effects and adjust the treatment plan as needed 2, 3.

References

Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

Research

Evidence-based treatment recommendations for OTC management of chronic constipation.

Journal of the American Association of Nurse Practitioners, 2022

Research

Management of chronic constipation in adults.

United European gastroenterology journal, 2017

Research

Chronic constipation: current treatment options.

Canadian journal of gastroenterology = Journal canadien de gastroenterologie, 2011

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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