Reviewed on 8/25/2021

What Is Lactulose and How Does It Work?

Lactulose is a prescription drug used by mouth or rectally to treat or prevent complications of liver disease (hepatic encephalopathy). It does not cure the problem, but may help to improve mental status. Lactulose is a colonic acidifier that works by decreasing the amount of ammonia in the blood. It is a man-made sugar solution.

What Are Dosages of Lactulose?

Dosages of Lactulose:

Adult and Pediatric Dosages

Oral/Rectal solution

  • 10 g/15 ml


  • 10 g
  • 20 g

Dosage Considerations – Should be Given as Follows:



  • Solution: 15-30 ml (10-20 g) orally once daily; may be increased to 60 ml (40 g) once daily
  • Crystals: 10-20 g orally once daily; may increase to 40 g per day


  • 0.7-2 g/kg/day (1-3 ml/kg/day) orally in divided doses; not to exceed 40 g/day (60 ml/day)

Portal Systemic Encephalopathy

Adult Dosage:


  • 30-45 ml (20-30 g) orally every 6-8 hours, adjusted until 2-3 soft stools/day; if acute, may be given every 1-2 hours until 2-3 soft stools/day


  • 20-30 g (30-40 ml) orally every hour to induce rapid defecation; reduced to 20-30 g every 6-8 hours after defecation achieved; titrated to produce 2-3 soft stools/day
  • 300 ml (200 g) rectally with 700 ml water or normal saline, retained for 30-60 minutes; may be repeated every 4-6 hours; transition to oral treatment before the discontinuance of rectal administration

Pediatric Dosage:


  • Infants: 2.5-10 ml/day (1.7-6.67 g/day) orally in divided doses; titrated to produce 2-3 soft stools per day
  • Children and adolescents: 40-90 ml/day (26.7-60 g/day) orally in divided doses; titrated to produce 2-3 soft stools/day


Pancreatitis is inflammation of an organ in the abdomen called the pancreas. See Answer

What Are Side Effects Associated with Using Lactulose?

Side effects of lactulose include:

  • dehydration
  • diarrhea
  • excessive bowel activity
  • high blood sodium levels
  • low blood sodium levels
  • nausea
  • vomiting
  • abdominal cramping
  • abdominal distention
  • burping (belching)
  • gas (flatulence)

This document does not contain all possible side effects and others may occur. Check with your physician for additional information about side effects.

What Other Drugs Interact with Lactulose?

If your doctor has directed you to use this medication, your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with your doctor, health care provider, or pharmacist first.

  • Lactulose has no known severe interactions with other drugs.
  • Lactulose has no known serious interactions with other drugs.
  • Moderate interactions of lactulose include:
  • Lactulose has no known mild interactions with other drugs.

This information does not contain all possible interactions or adverse effects. Therefore, before using this product, tell your doctor or pharmacist of all the products you use. Keep a list of all your medications with you, and share this information with your doctor and pharmacist. Check with your health care professional or doctor for additional medical advice, or if you have health questions, concerns, or for more information about this medicine.

What Are Warnings and Precautions for Lactulose?


  • This medication contains lactulose. Do not take Enulose, Kristalose, Constulose or Generlac, if you are allergic to lactulose or any ingredients contained in this drug.
  • Keep out of reach of children. In case of overdose, get medical help or contact a Poison Control Center immediately.


Effects of Drug Abuse

  • No information available

Short-Term Effects

  • See "What Are Side Effects Associated with Using Lactulose?"

Long-Term Effects

  • See "What Are Side Effects Associated with Using Lactulose?"


  • Diabetes (preparation contains lactose and galactose)
  • Monitor for electrolyte imbalance when the drug is used for longer than 6 months or in patients predisposed to electrolyte abnormalities
  • Avoid using other laxatives concomitantly
  • Inadequate response possible when taken concomitantly with anti-infective

Pregnancy and Lactation

  • Lactulose use during pregnancy may be acceptable. Either animal studies show no risk, or human studies are not available or animal studies showed minor risks, and human studies were done and showed no risk
  • It is unknown if lactulose is distributed into breast milk; use with caution


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Medscape. Lactulose.

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