Compare lactulose vs. Metamucil

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

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Generlac (lactulose)

Prescription only

Metamucil (psyllium)

Over-the-counter
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.

Metamucil (psyllium) is a natural fiber that is cheap and effective at relieving constipation.

3.8/ 5 average rating with 454 reviewsforMetamucil
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.
  • Inexpensive and available over-the-counter.
  • Made from a natural product.
  • Using Metamucil (psyllium) has multiple benefits, including relieving constipation, lowering cholesterol, and making you feel full.
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.
  • Metamucil (psyllium) can take up to 72 hours to relieve constipation.
  • Not the best choice for people who have swallowing problems or can't drink lots of liquids.
  • Metamucil (psyllium) can cause gas and stomach cramps.
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Used for
Dosage forms
  • Liquid
  • Powder
  • Pill
  • Powder
Price
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Reviews
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454 reviews so far
71%
saidit'sworth it
45%
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 Metamucil (psyllium) 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
  • Blockage of small or large intestine
    • Age 60 or older
    • Cancer
    • Taking medicines that cause constipation
    • Limited liquid intake
  • Choking
    • Limited liquid intake
    • Swallowing problems
  • Serious allergic reaction
    • Hypersensitivity to psyllium
See more detailed risks and warnings