Generic Name and PRN Dosing for Miralax
The generic name for Miralax is polyethylene glycol 3350 (PEG 3350), and the standard PRN dose is 17 grams (approximately one heaping tablespoon) mixed in 4 to 8 ounces of liquid, taken once daily as needed. 1
Generic Name
- Miralax is the brand name for polyethylene glycol 3350 (PEG 3350), an osmotic laxative that works by drawing water into the intestinal lumen to soften stool and increase bowel movements 2, 3
Standard PRN Dosing
Dose and Administration
- 17 grams once daily is the FDA-approved dose for occasional constipation, mixed in 4 to 8 ounces of water, juice, soda, coffee, or tea 1, 4
- Each bottle is supplied with a dosing cup marked to contain 17 grams when filled to the indicated line, or approximately one heaping tablespoon 1
- Bowel movements typically occur within 2 to 4 days (48 to 96 hours) after initiating treatment 1
Critical Implementation Points
- Adequate fluid intake is essential - patients must maintain sufficient daily fluid intake beyond just the mixing liquid for PEG to work effectively 4
- The medication can be mixed with any beverage including water, juice, soda, coffee, or tea for palatability 1
- For PRN use, patients may discontinue after several satisfactory bowel movements occur 1
Duration of PRN Use
- PEG 3350 is FDA-approved for up to 2 weeks of continuous use for occasional constipation without physician direction 1
- Patients should not use for longer than 2 weeks unless directed by a physician 1
- If chronic constipation persists beyond occasional use, the American Gastroenterological Association recommends PEG 3350 as first-line therapy with strong recommendation and moderate certainty of evidence 2
Common Side Effects
- Expected side effects include abdominal distension, loose stools, flatulence, nausea, bloating, cramping, and diarrhea 4, 5
- Most adverse events are mild to moderate and consistent with expected laxative effects 4
- Occasionally, nausea, stomach fullness, or gas may occur 1