Kristalose, generic name lactulose, belongs to group of drugs known as Laxatives. Kristalose is used for treating constipation. Kristalose may also be used for other purposes as determined by a physician. Kristalose works by drawing water into the colon, this then increases the pressure in the colon to stimulate bowel movements. Patients who are allergic to any ingredient found in Kristalose should avoid using it.