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Lactulose is a laxative used to treat constipation. This medication helps increase the number of bowel movements per day. Lactulose is an acidifier that works by increasing the stool moisture and softening the stool. It is a man-made sugar solution.

Lactulose may also be used for treatment or prevention of certain brain conditions that cause liver failure – which can lead to confusion, memory or thinking problems, behavioral changes, tremors, irritability, sleep disturbances, loss of coordination, and reduced brain power.

In addition, this medication may also be used for other purposes.

Dosage Considerations for Lactulose

Do not increase or decrease your dose without your doctor’s approval. If you miss a dose of Lactulose, take it as soon as you remember.

If it is near the time of the next dose, it is best to skip the missed dose of Lactulose. Use the next dose at the usual time. Do not double up on a dose to make up for the previous dose.

Condition: Chronic Constipation

  • Dosage for adults: take 15 mL once a day.
  • Dosage for children: Take 0.7 to 2 g / kg / day (1 to 3 mL / kg / day) in divided doses daily. Generally recommended not to exceed the maximum limit for adult–which is 40g / day (60 mL / day). 

Condition: Acute Constipation

  • Dosage for adults: take 15 mL once a day. Treatment should  be continued until bowel function returns to normal.

Condition: Hepatic Encephalopathy

  • Dosage for adults: Take 30 mL 3 times daily, or 300 mL in 700 mL water or normal saline as an enema for 30 to 60 minutes every 4 to 6 hours.
  • Maintenance dosage for adults: Take 30 to 45 mL 3 times a day.
  • Dosage for infants: Take 1.7 to 6.7 g / day (2.5 to 10 mL) daily, divided into 3 to 4 doses. Adjust dosage to produce 2 to 3 soft stools per day.
  • Dosage for children: Take 26.7 to 60 g / day (40 to 90 mL) daily, divided into 3 to 4 doses. Adjust dosage to produce 2 to 3 soft stools per day

Guidelines for Lactulose

Use Lactulose according to the directions on the product package or as directed by your doctor. Here’s how Lactulose should be used: 

  • Use this medication at the dosage recommended by your doctor – do not take it more than than recommended. 
  • Measure the medicine with a special measuring spoon or cup, not a household spoon. If you do not have a special measuring device, check with your pharmacist.
  • The liquid form of Lactulose may be slightly darker in color – however, it is not dangerous. Do not use the medication if it is very dark, has become thicker in texture, or is thinner.
  • Lactulose powder should be mixed with at least 4 ounces of water. You can also use fruit juice or milk to make the medicine taste better when taken by mouth.
  • It may take up to 48 hours before you have a bowel movement after taking Lactulose.
  • If you have been using Lactulose for a long time, your doctor may want you to have occasional blood tests. Don’t miss scheduled appointments.
  • Store Lactulose at room temperature and away from moisture and heat.

What is Lactulose Used For

Lactulose can be used for treatments of: 

  • Chronic constipation
  • Acute constipation
  • Hepatic encephalopathy – a condition that causes a temporary decrease in brain function in people with liver disease. When the liver is damaged, it cannot remove toxic substances from the blood.

Contraindications for Lactulose

Since lactulose solution contains galactose less than 1.6 g/15 mL, this medicine is contraindicated in patients undergoing or requiring a low galactose diet.


Below are some important precautions you should know before using Lactulose:

  • Before taking Lactulose, tell your doctor or pharmacist if you are allergic to it or if you have any other allergies. This product may contain inactive ingredients which can cause allergic reactions or other problems.
  • This medication should not be used if you have certain medical conditions. Before using this medication, consult your doctor or pharmacist if you have: a diet low in galactose (for example, reduced dairy consumption) and certain intestinal problems (such as bowel obstruction).
  • Before using this medication, tell your doctor or pharmacist about your medical history, particularly if you have diabetes.
  • The elderly  may be at greater risk for blood mineral loss while using this medicine, especially if they are using it for a long time. 
  • Do not take other laxatives while using this medicine. Frequent or excessive use of laxatives can lead to dehydration. This is very likely to happen to children or the elderly. Tell your doctor right away if you experience any of the symptoms of dehydration, such as muscle weakness, muscle cramps, and dizziness.
  • Before having surgery or other procedures, tell your doctor or surgeon that you are using this medication. 
  • This medicine contains different sugars. If you have diabetes, this medicine may affect your blood sugar. Check your blood sugar regularly as directed and share the results with your doctor. Your doctor may need to adjust your medications, exercise program, or diet plan. 
  • During pregnancy, use this medication only when clearly needed. Discuss the risks and benefits with your doctor.
  • It is unknown whether this drug passes into breast milk. Consult your doctor before breastfeeding.

Lactulose Drug Interactions

Your doctor or pharmacist may already be aware of possible drug interactions and may be monitoring your condition. Do not start, stop or change the dose of any medicine before consulting your doctor first. 

Before using Lactulose, tell your doctor or pharmacist about any current prescription, nonprescription products, or herbal medicines you are using, such as antacids containing aluminum, magnesium, and other laxatives. Inform your doctor and pharmacist all your medications.

List of Lactulose Side Effects 

Get emergency medical help if you have any of the signs of an allergic reaction, such as:

  • Itchy rash
  • Difficulty breathing
  • Swelling of the face, lips, tongue, or throat

Stop using Lactulose and tell your doctor immediately if you experience severe or persistent diarrhea.

Mild side effects of Lactulose include:

  • Diarrhea
  • Stomach upsets
  • Nausea or vomiting
  • Feeling bloated or passing gas

Book an appointment with your doctor or pharmacist through Smarter Health to find out more about the recommended dosage for lactulose and its proper use based on your condition. Smarter Health allows you to access healthcare services whenever you need them. Be sure to try out our teleconsultation service right away.

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