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Medical and Pharmacy Editor:

Brand Name: Enulose, Kristalose, Constulose, Generlac

Generic Name: Lactulose

Drug Class: Laxatives, Osmotic; Ammonium Detoxicants

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.

Lactulose is available under the following different brand names: Enulose, Kristalose, Constulose, and Generlac.

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 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
Medically Reviewed by a Doctor on 5/15/2017

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