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Generic Name

lactulose (LACT u los)


Trade Name



What is lactulose?

Lactulose is a sugar which is not metabolized and absorbed by the body. Rather, the bacteria in the colon or large bowel break this sugar down into acids. These acids, in turn, pull water into the colon and soften the stool. Another thing that happens is that ammonia then moves from the blood into the colon. In patients with cirrhosis of the liver, it lowers ammonia in the blood and thereby reduces the mental changes of sluggishness, confusion and mental wandering.


What is it used for?

Lactulose is used to treat constipation and the mental changes that can occur when cirrhosis of the liver is severe.


How do I take it?

Follow your physician’s instructions carefully. The medication may be mixed with fruit juice, water or milk. Drink 8 ounces or more of liquid with each dose. Store it at room temperature away from heat or light. Do not freeze. The liquid may darken in color which does not effect the medication. Keep all medications away from children. Never share your medications with anyone else.


What do I do for a missed dose?

If you miss a dose of this medicine, take it as soon as possible. If it is almost time for your next dose, skip the missed dose and return to your regular schedule. Do not double up on this medication.


Are there interactions with food or beverages?

There are no known interactions with food or beverages. Drinking more water is recommended and a diet rich in fiber or bran can improve the effectiveness of this drug.


Are there interactions with other drugs?

An interaction generally means that one drug may increase or decrease the effect of another drug. Also, the more medications a person takes, the more likely there will be a drug interaction. Antacids can be used but they should not be taken at the same time as lactulose.

Interactions with this drug may occur with the following:

  • other laxatives
  • neomycin
  • antibiotics
  • diabetic medications


Is there a problem if I have another disorder or disease?

At times, a drug may have a different or enhanced effect when other diseases are present. At other times, the drug may worsen or effect another disease. Since lactulose syrup also contains other sugars such as lactose and galactose, patients with diabetes should consult their physicians.


What about allergies?

People who have known allergies or asthma may be at an increased risk for a reaction from any new medication. The physician should always know a patient’s allergy history. Signs of an allergic reaction are skin rash, hives and itching. Of course, a person should not take lactulose if there has been a previous reaction to this or a similar drug.


What if I’m pregnant, considering pregnancy or breast-feeding?

Most females now know that, if possible, no drug, including alcohol, should be taken during pregnancy or lactation. The potential danger, of course, is an injury to the baby. However, some drugs are much safer than others in this regard. So, the FDA has a grading system for each drug which reflects what is known medically. It ranks drugs from A, where medical studies show no evidence for danger to the fetus or mother, to B, C, D and X, where the medical evidence indicates that the risk to the fetus outweighs any benefit to the mother. Lactulose is ranked B. Always consult your physician before taking any drug during or when planning pregnancy.


What are the effects on sexual function?

There are no known adverse effects of lactulose on sexual function.


Are there other precautions?

If you are a diabetic check with your physician if you experience symptoms of high blood sugar (excessive thirst or urination, nausea, vomiting or “fruity” breath).


How long is it safe to take lactulose?

Lactulose is safe to take long-term.


How about side effects?

Adverse reactions can occur with any drug, even over-the-counter medications. Some of these are mild such as a stomach upset, which may be avoided by taking the medication with food. Minor reactions may go away on their own but if they persist, contact the physician. For major reactions, the patient should contact the physician immediately.

For lactulose, the following are the observed side effects:


  • belching
  • bloating
  • diarrhea
  • crampy abdominal pain
  • nausea
  • vomiting


  • severe weakness
  • faintness
  • severe diarrhea


A physician’s comment..

Lactulose can be effective in treating chronic constipation, especially if it is taken together with a high fiber diet. The dose needs to be adjusted so that the desired stool formation and softening is obtained. It is also effective in reversing subtle mental changes that may occur with liver cirrhosis.