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Related to Constilac: Lactulose, Duphalac


a synthetic disaccharide used as a cathartic and to enhance the excretion of ammonia in treatment of hepatic encephalopathy.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.


Apo-Lactulose (CA), Constulose, Duphalac (UK), Enulose, Euro-Lac (CA), Generlac, Gen-Lac (CA), GPI-Lactulose (CA), Kristalose, Lactugal (UK), Lactulax (CA), Lemlax (UK), PMS-Lactulose (CA), Ratio-Lactulose (CA), Regulose (UK)

Pharmacologic class: Osmotic

Therapeutic class: Laxative

Pregnancy risk category B


Produces osmotic effect, which increases water content in colon and enhances peristalsis. Breakdown products in colon lead to acidification of colonic contents, softening of feces, and decreased ammonia absorption from colon to systemic circulation. These effects reduce blood ammonia level in portal-system encephalopathy.


Powder (single-use packets): 10 g, 20 g

Syrup: 10 g/15 ml

Indications and dosages


Adults: 10 to 20 g (15 to 30 ml) P.O. daily; may increase to 60 ml daily p.r.n.

Portal-system encephalopathy

Adults: 20 to 30 g (30 to 45 ml) P.O. three or four times daily until two or three soft stools are produced daily. Therapy may continue over long term. Or, 300 ml P.O. with 700 ml of water or normal saline solution. Or, as retention enema by rectal balloon catheter, repeated q 4 to 6 hours.


• Patients requiring low-galactose diet


Use cautiously in:

• diabetes mellitus

• elderly patients

• pregnant or breastfeeding patients

• children.


• Don't give concurrently with other laxatives.

• Dissolve contents of single-use packet in 4 oz of water or juice.

• Dilute syrup with water or fruit juice to mask taste.

Adverse reactions

GI: nausea, vomiting, diarrhea, intestinal cramps, abdominal distention, flatulence

Metabolic: hyperglycemia (in diabetic patients), hypokalemia, hypernatremia


Drug-drug. Anti-infectives: decreased lactulose efficacy

Other laxatives: interference with response to lactulose (in patients with hepatic encephalopathy)

Drug-diagnostic tests. Blood ammonia: 25% to 50% decrease

Glucose: increased level (in diabetic patients)

Potassium: decreased level

Sodium: increased level

Patient monitoring

• Watch for adverse GI reactions.

• Check stool consistency and frequency.

• Monitor electrolyte levels, especially in elderly patients.

• Check blood glucose level in diabetic patients.

Patient teaching

• Instruct patient to dissolve contents of single-use packet in 4 oz of water or juice.

• Suggest that patient dilute syrup with water or juice to mask taste.

• Tell patient drug may cause flatulence and intestinal cramps at first, but these symptoms usually subside.

• Inform patient that excessive use may cause diarrhea and excessive fluid loss.

• Encourage patient to drink adequate fluids and to report signs and symptoms of dehydration.

• As appropriate, review all other significant adverse reactions and interactions, especially those related to the drugs and tests mentioned above.

McGraw-Hill Nurse's Drug Handbook, 7th Ed. Copyright © 2013 by The McGraw-Hill Companies, Inc. All rights reserved


A synthetic disaccharide used to treat hepatic encephalopathy and chronic constipation.
Farlex Partner Medical Dictionary © Farlex 2012


A synthetic disaccharide used to treat hepatic encephalopathy, which is administered by mouth, acting as a laxative; lactulose reduces intraluminal NH3 which, via the extracellular fluid, reduces NH3 in the blood.
Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.


A synthetic disaccharide used to treat hepatic encephalopathy and chronic constipation.
Medical Dictionary for the Health Professions and Nursing © Farlex 2012


A disaccharide sugar that acts as a gentle but effective LAXATIVE. It is not absorbed or broken down but remains intact until it reaches the colon where it is split by bacteria and helps to retain water, thereby softening the stools. Brand names are Duphalac, Lactugal and Regulose.
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005