A Patient's Guide to Lactulose Solution

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Lactulose solution is a type of drug known as a colonic acidifier. It is a sugar solution that is man-made. It is prescribed to help promote bowel movements. It is also prescribed under several brand names including Kristalose, Chronulac, Evalose, Constilac, Duphalac, and Constulose.


This medication is a laxative. It helps to increase how many bowel movements a patient has per day as well as how many days they have bowel movements, resulting in the alleviation of constipation. It helps to soften stools by increasing the water content in stools. This medication may also be prescribed to prevent or treat hepatic encephalopathy (liver disease).


This medication is typically taken once a day and it is taken by mouth. Patients can mix it with water, soft desserts, fruit juice, or milk to help improve its’ taste. Patients using the crystals in packets should pour the crystals into four ounces of water and let them fully dissolve, and then drink it. This medication should be taken each day at the same time for best results. The dose a patient is prescribed will depend on their response to therapy and their medical condition. Most patients will have a bowel movement within 48 hours, but it can take up to 48 hours.


Patients with certain medical conditions may not be able to take this medication. All patients should tell their doctor about all medical conditions prior to starting this medication. The contraindicated medical conditions include diabetes, bowel obstruction, other bowel problems, and allergies.

Side Effects

Patients taking lactulose solution may experience side effects. The common side effects tend to decrease with time and warrant no medical intervention unless they worsen or persist, but the serious side effects often warrant immediate medical attention. The common side effects include cramps, gas, nausea, bloating, stomach pain/rumbling, and burping. The serious side effects include seizures, diarrhea, mood/mental changes, vomiting, irregular heartbeat, and weak/cramping muscles.

Drug Interactions

Certain medications may adversely interact with this medication. This can lead to complications and some can be very dangerous. The medications that may interact with this medication include laxatives, and antacids that contain magnesium or aluminum. Patients should tell their doctor about every medication or drug they take including other prescription medications, nutritional supplements and vitamins, herbal products, and over-the-counter medications.

Risks and Warnings

Patients on a low galactose diet may not be able to take this medication. A low galactose diet is a type of diet in which the patient cannot consume milk products or they can only consume very little milk products. Elderly patients are at risk for experiencing blood-mineral losses when taking this medication, especially if they take it for prolonged periods of time. Patients using other laxatives in conjunction with this drug are at risk of experiencing severe dehydration. Those who are breastfeeding or pregnant may have to avoid this medications.


RxList (2009). Lactulose Solution. Retrieved on October 31, 2009 from Website: https://www.rxlist.com/lactulose-solution-drug.htm