Compare lactulose vs. Miralax

Head-to-head comparisons of medication uses, side effects, ratings, and more.

Generlac (lactulose)

Prescription only
Relieves constipation and gets rid of ammonia in people with liver problems.

Generlac (lactulose) relieves constipation and high ammonia levels, but it can take up to 48 hours to work.

Helps get things moving.

Miralax (Polyethylene Glycol) provides effective relief of constipation without "cramping" your style.

4.0/ 5 average rating with 226 reviewsforMiralax
Upsides
  • Generlac (lactulose) is the first-choice treatment for brain conditions caused by high ammonia levels.
  • Can be used if you have severe chronic constipation leading to blockage.
  • Available in generic.
  • Can be taken orally or rectally.
  • Miralax is the most recommended laxative by pharmacists and doctors.
  • Most people felt it was worth the hassle.
  • It's gluten and sugar free.
  • It causes little to no cramping, bloating, gas, or feelings like you "have to go right now" compared to some other medicines to treat constipation.
  • Works differently than other over-the-counter laxatives so it's a great alternative if other medicines haven't worked.
Downsides
  • Should not be used if you are on a galactose-restricted diet.
  • Does not provide rapid relief of constipation. Talk to your doctor or pharmacist if you need quick relief.
  • Generlac (lactulose) has a very sweet flavor that most people don't like.
  • You have to dissolve Miralax in a beverage and drink it versus taking a pill.
  • It's not for children 16 years or younger.
  • Miralax doesn't work overnight. It can take up to 2-4 days to have a bowel movement.
  • It's not recommended that you take it for more than a week, so it you haven't had any success, you'll need to call your doctor for other laxative options.
Used for
Dosage forms
  • Liquid
  • Powder
  • Liquid
Price
No pricing information available
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Reviews
Not enough review data.Leave a review
226 reviews so far
75%
saidit'sworth it
54%
saiditworked well
10%
saidit'sa big hassle

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Side effects
The Generlac (lactulose) FDA package insert doesn’t have numbers about how common side effects are.
The Miralax (Polyethylene Glycol) FDA package insert doesn’t have numbers about how common side effects are.
Risks and risk factors
  • Mineral imbalances
    • Taking Generlac (lactulose) for more than 6 months
    • Elderly
    • Taking medications that cause mineral imbalance
    • Not exercising regularly
  • Increased blood sugar
    • Diabetes
  • Problems during colonoscopy
See more detailed risks and warnings
  • Electrolyte imbalance
    • Taking with medications that cause electrolyte imbalance
    • Age 60 or older
  • Risk to fetus
    • Women of childbearing age
  • Bowel blockage
    • Age 60 or older
    • Malignancy
    • Other condition that causes blockage or narrowing of bowel
    • Taking medications that cause constipation
See more detailed risks and warnings