Side Effects of Movicol (Polyethylene Glycol 3350)
The most common side effects of Movicol include abdominal pain/cramping, bloating, nausea, diarrhea, flatulence, and anal irritation, with gastrointestinal symptoms typically being mild and decreasing markedly after the first week of treatment. 1, 2, 3
Most Frequent Gastrointestinal Side Effects
The FDA-approved labeling identifies the following common adverse effects 3:
- Nausea - occurs frequently but is typically mild and resolves without intervention 2, 3
- Abdominal cramping and bloating - particularly common during initial treatment, though symptoms decrease substantially after the first week 1, 2, 3
- Diarrhea - significantly more common with PEG than placebo (158 additional cases per 1,000 patients treated), especially with higher doses 1, 3
- Flatulence and stomach fullness - reported as occasional side effects 1, 3
- Anal irritation - may occur with frequent bowel movements 2
Important Clinical Context on Tolerability
When used for IBS-C specifically, abdominal pain is noted as the most frequent adverse event and a common side effect that may limit use. 4 This is particularly relevant since IBS patients already experience baseline abdominal pain, making this side effect more clinically significant in this population.
The temporal pattern of side effects is reassuring: gastrointestinal adverse events decrease markedly after the first week of treatment in patients taking PEG 3350 5. This suggests that initial side effects often resolve with continued use.
Rare but Important Reactions
- Allergic reactions - hives and skin rashes have been reported on rare occasions, suggestive of hypersensitivity 3
- If allergic symptoms develop, discontinue the medication immediately and contact a physician 3
Serious Adverse Events
No deaths or serious adverse events requiring treatment discontinuation were reported in clinical trials 6, 5. Laboratory evaluations found no adverse effects from treatment, and PEG 3350 does not cause significant net gain or loss of sodium and potassium 2, 7.
Key Safety Advantages
PEG 3350 has a favorable safety profile because it is minimally absorbed systemically. 2 This distinguishes it from other laxative classes and contributes to its tolerability for long-term use up to 6 months 1.
Critical Warnings and Contraindications
- Do not use if symptoms of bowel obstruction are present (nausea, vomiting, abdominal pain or distention) 3
- Prolonged, frequent, or excessive use may result in electrolyte imbalance and laxative dependence 3
- Should be used for 2 weeks or less unless directed by a physician for chronic conditions 3
- Taking more than the prescribed dose may cause severe diarrhea and fluid loss 3
Special Populations
- Geriatric patients: Higher incidence of diarrhea occurred at the standard 17 g dose in nursing home patients; if diarrhea develops, discontinue PEG 3350 3
- Pregnancy: Category C - should only be used if clearly needed 3
- Pediatric use: Safety and effectiveness not established in FDA labeling, though research studies show good tolerability with diarrhea as the only reported adverse effect in 9 patients 3, 8