Complications of Miralax (Polyethylene Glycol 3350)
The most common complications of Miralax (polyethylene glycol 3350) include nausea, bloating, abdominal cramps, flatulence, and diarrhea, which are generally mild and transient. 1, 2
Common Side Effects
- Nausea occurs frequently but is typically mild and resolves without intervention 1, 3
- Abdominal bloating and cramping are common, especially during initial treatment 1, 2
- Flatulence (gas) may occur as a result of the osmotic action 3, 4
- Diarrhea can develop, particularly with higher doses or in sensitive individuals 1, 4
- Anal irritation may occur with frequent bowel movements 1, 2
Rare but Serious Complications
- Allergic reactions including hives and skin rashes have been reported, though these are rare 3
- Electrolyte imbalances may occur with prolonged, frequent, or excessive use 3, 4
- In elderly nursing home patients, a higher incidence of diarrhea has been observed at the standard 17g dose 3
Special Populations and Contraindications
- Contraindicated in patients with bowel obstruction or ileus 1, 3
- Should not be used in patients with known hypersensitivity to polyethylene glycol 3
- Not FDA-approved for use in children, though clinical studies have shown efficacy and safety in pediatric populations 3, 5
- Should be used with caution in pregnant women and only if clearly needed (Pregnancy Category C) 3
Dosing Considerations to Minimize Complications
- Standard dose is 17g daily, which should be dissolved in 4-8 ounces of liquid 3
- Higher doses (up to 68g) may increase the risk of diarrhea but have been used safely for rapid relief of constipation 6
- Treatment duration should generally be limited to 2 weeks unless directed by a physician 3
- Adequate hydration should be maintained during treatment to prevent dehydration 2, 3
Laboratory Abnormalities
- No clinically significant effects on laboratory tests have been demonstrated with standard use 3, 4
- No significant changes in serum electrolytes, calcium, glucose, BUN, creatinine, or serum osmolality have been observed even with higher doses 6
Medication-Specific Considerations
- Unlike some other laxatives, PEG 3350 does not cause significant net gain or loss of sodium and potassium 2
- PEG 3350 is minimally absorbed systemically, which contributes to its favorable safety profile 2, 3
- When used for bowel preparation for colonoscopy, higher volumes are required which may increase the risk of side effects 1
Understanding these potential complications can help patients and providers monitor for adverse effects and adjust treatment as needed.