Lactulose is a medication used to treat constipation and reduce the amount of ammonia in the blood of patients with liver disease. It is a synthetic sugar that is broken down in the colon into products that pull water out from the body and into the colon, which softens stools and increases bowel movements. Lactulose is available as a liquid to be taken by mouth, and the dosage and frequency of use depend on the condition being treated. It is also available as an enema for rectal use in the treatment of liver disease. Lactulose is generally safe to use, but some common side effects include diarrhea, bloating, and wind. Before taking lactulose, it is important to inform your doctor and pharmacist of any allergies, medications, or medical conditions you have.