lactulose vs polyethylene glycol 3350
PlainMeds reviewed this comparison against our methodology in August 2026. It places FDA and CMS record fields side by side, without recommending either medication.
Side-by-side comparison of lactulose and polyethylene glycol 3350. Data from FDA drug databases (Orange Book, NDC Directory, recalls, shortages) covering 20,000+ approved drugs, plus CMS pricing; see our methodology.
Enulose, Kristalose
MiraLAX
Lactulose is a medicine that helps treat and prevent problems with your brain caused by liver disease. It works by reducing the amount of ammonia in your blood.
MiraLAX is a laxative medicine. It helps to relieve constipation by drawing water into your stool, making it easier to pass.
This medicine treats and prevents portal-systemic encephalopathy. This condition can happen when your liver isn't working well. Lactulose helps lower ammonia levels in your blood, which can improve your mental state and brain function.
MiraLAX treats occasional constipation, which means you have irregular bowel movements. It usually helps you have a bowel movement within 1 to 3 days. Do not use for more than 7 days.
Lactulose is a sugar that is not digested in your body. It travels to your colon where it is broken down by bacteria. This process makes the colon more acidic, which helps to draw ammonia from the blood into the colon, where it is then removed from the body through bowel movements.
MiraLAX is an osmotic laxative. It works by drawing water into your colon. This softens the stool and makes it easier to pass, relieving constipation.
- • Gas
- • Bloating
- • Belching
- • Abdominal discomfort
- • Cramping
- • Diarrhea
- • Nausea
- • Headache
- • Abdominal pain
- Nausea 2,524
- Constipation 2,497
- Fall 2,241
- Vomiting 2,047
- Fatigue 2,027
- Diarrhoea 6,828
- Nausea 5,306
- Constipation 5,098
- Fatigue 4,564
- Vomiting 3,284
If you need a low-galactose diet, you should not take this medicine. Lactulose solution contains galactose.
Do not use more than directed unless your doctor tells you to. Ask a doctor if you are 16 years old or younger.
Tell your doctor if you are pregnant or breastfeeding before taking this medicine. It is not known if lactulose can harm your unborn baby. It is also not known if lactulose passes into breast milk.
It is not known if MiraLAX is safe to use during pregnancy or while breastfeeding. Talk to your doctor before using this medicine if you are pregnant or breastfeeding.
How to Read This lactulose vs polyethylene glycol 3350 Comparison
lactulose is classified in the Osmotic Laxative drug class, while polyethylene glycol 3350 sits within the Osmotic Laxative class. Because both drugs share the same classification, they are often considered interchangeable in theory, but clinical outcomes rarely track that cleanly. Both drugs are split between OTC and prescription status, which affects access and supervision.
Adverse event totals above are pulled from the FDA's Adverse Event Reporting System (FAERS). For these top-ranked reactions alone, lactulose has 11,336 submissions while polyethylene glycol 3350 has 25,080. Those figures reflect cumulative reporting volume, not per-patient risk, so older, widely dispensed drugs typically look worse on count alone. No direct interaction between these two drugs is listed in our FDA-derived dataset, though co-prescription still warrants pharmacist review. Serious warnings, pregnancy guidance, and contraindications can differ even when indications overlap.
A table cannot represent individual circumstances. Data here is sourced from FDA Structured Product Labels (SPL) and FAERS, both of which update as manufacturers and clinicians submit new information. This registry does not provide medical, treatment, substitution, or medication-change directions for lactulose or polyethylene glycol 3350.
Registry boundary: This comparison displays source-record fields and does not provide individualized medical direction.