Recommended Dosing and Duration of Polyethylene Glycol (PEG) 3350
For chronic constipation, PEG 3350 should be administered at a dose of 17 g once daily mixed in 8 ounces of liquid, with demonstrated efficacy for up to 6 months of continuous use. 1, 2
Dosing for Constipation
- PEG 3350 is FDA-approved at a dose of 17 g daily for the treatment of occasional constipation and is widely available over-the-counter 1
- The standard formulation contains 17 g of PEG 3350 per dose (cap filled to the top) 2
- PEG generally produces a bowel movement within 1-3 days of administration 2
- Response to PEG has been shown to be durable over 6 months of continuous use 1
- For chronic idiopathic constipation (CIC), PEG has demonstrated significantly better efficacy than placebo in increasing complete spontaneous bowel movements (CSBMs) and spontaneous bowel movements (SBMs) 1
Dosing for Bowel Preparation
For colonoscopy preparation, two main regimens are recommended:
For split-dose regimens, the second portion should begin 4-6 hours before colonoscopy and be completed at least 2 hours before the procedure (strong recommendation, moderate-quality evidence) 1
For morning colonoscopies, split-dose regimens are generally preferred over same-day dosing for optimal bowel preparation quality 1
For afternoon colonoscopies, same-day dosing is an acceptable alternative 1
Special Considerations
In pediatric patients, a 1-day PEG 3350 bowel preparation regimen has been shown to be safe and effective (93% success rate) 3
For severe constipation or fecal impaction, higher doses may be required - up to eight 13.8 g sachets of PEG with electrolytes (approximately 1L) per day for up to three days 4
For low-risk patients undergoing colonoscopy, a same-day single dose of 2L PEG has been shown to be non-inferior to standard split-dose regimens, with fewer adverse events 5
Potential Side Effects
- Common side effects include abdominal distension, loose stool, flatulence, and nausea 1
- Diarrhea is more common with PEG than placebo (158 more per 1,000 patients) 1
- Most adverse events are mild to moderate in severity and consistent with expected laxative effects 6
Implementation Tips
- A trial of fiber supplement can be considered for mild constipation before PEG use or in combination with PEG 1
- For chronic constipation, PEG can be used for extended periods (up to 6 months) with sustained efficacy 1, 6
- When using PEG for bowel preparation, the timing between the last dose and colonoscopy is critical - every additional hour between purgative completion and colonoscopy decreases preparation quality by approximately 10% 1
- For optimal results, PEG should be taken with adequate fluid (8 ounces per dose) 1, 7