Lactulose

pronounced as (lak' tyoo lose)

Brand Name(s): Cholac®, Constilac® Syrup, Constulose®, Enulose®, Evalose®Syrup ¶, Generlac®, Heptalac®, Kristalose®, Laxilose®, Portalac®, also available generically
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Why is this medicine prescribed?

Lactulose is a synthetic sugar used to treat constipation. It is broken down in the colon into products that pull water out from the body and into the colon. This water softens stools. Lactulose is also used to reduce the amount of ammonia in the blood of patients with liver disease. It works by drawing ammonia from the blood into the colon where it is removed from the body.

This medication is sometimes prescribed for other uses; ask your doctor or pharmacist for more information.

How should this medicine be used?

Lactulose comes as liquid to take by mouth. It usually is taken once a day for treatment of constipation and three or four times a day for liver disease. Your prescription label tells you how much medicine to take at each dose. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take lactulose exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor.

What special precautions should I follow?

Before taking lactulose,

  • tell your doctor and pharmacist if you are allergic to lactulose or any other drugs.
  • Tell your doctor and pharmacist what prescription and nonprescription medications, vitamins, nutritional supplements, and herbal products you are taking or plan to take while taking lactulose. Your doctor may need to change the doses of your medications or monitor you carefully for side effects.
  • tell your doctor if you have diabetes or require a low-lactose diet.
  • tell your doctor if you are pregnant, plan to become pregnant, or are breast-feeding. If you become pregnant while taking lactulose, call your doctor.
  • if you are having surgery or tests on your colon or rectum, tell the doctor that you are taking lactulose.

What should I do if I forget to take a dose?

Take the missed dose as soon as you remember it. However, if it is almost time for the next dose, skip the missed dose and continue your regular dosing schedule. Do not take a double dose to make up for a missed one.

What side effects can this medicine cause?

Lactulose may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:

  • diarrhea
  • gas
  • nausea

If you have any of the following symptoms, stop taking lactulose and call your doctor immediately:

  • stomach pain or cramps
  • vomiting

If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration's (FDA) MedWatch Adverse Event Reporting program online ( https://www.fda.gov/Safety/MedWatch ) or by phone (1-800-332-1088).

What should I know about storage and disposal of this medication?

Keep this medication in the container it came in, tightly closed, and out of reach of children. Store it at room temperature and away from excess heat and moisture (not in the bathroom).

Dispose of unneeded medications in a way so that pets, children, and other people cannot take them. Do not flush this medication down the toilet. Use a medicine take-back program. Talk to your pharmacist about take-back programs in your community. Visit the FDA's Safe Disposal of Medicines website https://goo.gl/c4Rm4p for more information.

Keep all medication out of sight and reach of children as many containers are not child-resistant. Always lock safety caps. Place the medication in a safe location – one that is up and away and out of their sight and reach. https://www.upandaway.org

What other information should I know?

Keep all appointments with your doctor.

To improve the taste of lactulose, mix your dose with one-half glass of water, milk, or fruit juice.

Do not let anyone else take your medicine. Ask your pharmacist any questions you have about refilling your prescription.

Keep a written list of all of the prescription and nonprescription (over-the-counter) medicines, vitamins, minerals, and dietary supplements you are taking. Bring this list with you each time you visit a doctor or if you are admitted to the hospital. You should carry the list with you in case of emergencies.

¶ This branded product is no longer on the market. Generic alternatives may be available.

This report on medications is for your information only, and is not considered individual patient advice. Because of the changing nature of drug information, please consult your physician or pharmacist about specific clinical use.

The American Society of Health-System Pharmacists, Inc. represents that the information provided hereunder was formulated with a reasonable standard of care, and in conformity with professional standards in the field. The American Society of Health-System Pharmacists, Inc. makes no representations or warranties, express or implied, including, but not limited to, any implied warranty of merchantability and/or fitness for a particular purpose, with respect to such information and specifically disclaims all such warranties. Users are advised that decisions regarding drug therapy are complex medical decisions requiring the independent, informed decision of an appropriate health care professional, and the information is provided for informational purposes only. The entire monograph for a drug should be reviewed for a thorough understanding of the drug's actions, uses and side effects. The American Society of Health-System Pharmacists, Inc. does not endorse or recommend the use of any drug. The information is not a substitute for medical care.

AHFS ® Patient Medication Information™. © Copyright, 2025. The American Society of Health-System Pharmacists ® , 4500 East-West Highway, Suite 900, Bethesda, Maryland. All Rights Reserved. Duplication for commercial use must be authorized by ASHP.

Selected Revisions: January 15, 2024.