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Lactulose is a synthetic disaccharide used primarily as a laxative and to treat hepatic encephalopathy.

Last Modified: 13 May 2024

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What is Lactulose? 

Lactulose is a synthetic disaccharide used primarily as a laxative and to treat hepatic encephalopathy. It is composed of galactose and fructose and works by drawing water into the bowel, which softens stools and stimulates bowel movements. 

Lactulose is produced by the isomerization of lactose, which involves rearranging the lactose molecules under alkaline conditions and heat. 

Global Name

Generic name: Lactulose
Brand name: Constulose, Enulose, Generlac, and Kristalose.


What is Lactulose used for? 

Lactulose is used to treat chronic constipation and to reduce the levels of ammonia in patients with hepatic encephalopathy, a condition associated with severe liver disease. 

How do you use Lactulose? 


Lactulose is available as an oral solution and in powder form which can be dissolved in water. 

Dosage information: 

  • For Constipation: 
    • Adults and Children aged 14 years and older: 15-30 mL daily. 
    • Children aged 7-14 years: 15 mL daily. 
    • Children aged 1-6 years: 5-10 mL daily. 
    • Infants under 1 year: 2.5 mL daily. 
  • For Hepatic Encephalopathy: 
    • Adults: The dose may range from 30-45 mL three to four times daily, adjusted as needed. 


  • Children: Yes, with adjusted dosages. 
  • Adults: Yes. 
  • Elderlies: Yes, with caution if they have other health issues.  
  • Pregnancy and Lactation: Generally considered safe but should be taken under medical supervision. 
  • Individuals with a known allergy to lactulose or its components should avoid this medication. 
  • Patients with galactosemia 

Warnings and precautions:

  • Lactulose should be taken with caution by diabetic patients due to its sugar content. 
  • It may be taken with or without food. 
  • Prolonged use may lead to dehydration and electrolyte imbalance 

Drug and Food Interactions 

  • Antacids should not be taken within 2 hours of lactulose, as they may alter its pH and reduce its efficacy. 
  • There are no major food interactions, but it is advisable to consume it on an empty stomach for faster results. 

Side Effects

Common side effects include diarrhea, bloating, gassiness, and abdominal discomfort. 

Pharmacist Tips

  • Understanding Your Medication:

Recognise that Lactulose is a gentle yet effective laxative and also helps manage hepatic encephalopathy by lowering ammonia levels.

  • Managing Expectations:

Lactulose can take 1 to 2 days to effect normal bowel movements.

  • Dosage Precision:

Use the measuring cup or spoon provided with  the Lactulose solution to ensure you take the correct dose.

  • Dietary Considerations:

Stay hydrated and maintain a diet high in fiber while using Lactulose to enhance its effectiveness.

  • Side Effects Management:

If you experience bloating or flatulence, these are common side effects that often resolve with continued use. Should you encounter diarrhea, contact your healthcare provider, as your dose may need adjustment.

  • Monitoring Health:

Inform your doctor if you have diabetes since Lactulose contains sugars that can affect blood glucose levels. For patients with lactose intolerance, Lactulose may cause symptoms due to its chemical structure similar to lactose.

  • Medication Adherence:

Do not stop taking Lactulose abruptly without consulting your healthcare provider, especially if you're taking it for hepatic encephalopathy.

  • Avoiding Overuse:

Overuse of any laxative, including Lactulose, can lead to dependence or worsen constipation.

  • Traveling Tips:

When traveling, pack Lactulose in your carry-on luggage to avoid missed doses due to lost checked baggage.

  • Emergency Information:

Be aware of signs of an electrolyte imbalance, such as weakness, confusion, or irregular heartbeat, and seek immediate medical attention if these symptoms occur.

  • Communication with Healthcare Providers:

Always inform healthcare providers about your Lactulose use, particularly if you're scheduled for any medical procedures or tests.

  • Safety Precautions:

Keep Lactulose out of reach of children and pets to prevent accidental ingestion. 


Where is Lactulose available in Hong Kong?

Lactulose is an over-the-counter (OTC) medication that can be sold without a prescription. Topical preparations can be bought over-the-counter, but oral and injectable forms require a prescription.


Is Lactulose for purchase over-the-counter?

Yes, lactulose is available over-the-counter, but it's recommended to use under medical advice, especially for long-term use.

How long does it take for Lactulose to work?

It can take 24-48 hours for lactulose to have a laxative effect.

Can Lactulose be taken during pregnancy?

Lactulose is considered safe during pregnancy but should be used under the supervision of a healthcare provider.

Why is Lactulose contraindicated in bowel obstruction?

Lactulose is contraindicated in bowel obstruction because its osmotic laxative effect could increase bowel movement and pressure within the intestines, potentially worsening the obstruction and risking serious complications like bowel wall ischemia or perforation. 

This website provides content related to drug use and medicine for informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Do not use the information on this website to diagnose or treat a health problem or disease without consulting a qualified healthcare provider. The website's owners and contributors are not liable for any repercussions, adverse effects, or consequences resulting from the use of any medication or information provided herein.

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