Lactulose is an osmotic laxative. It is used for the relief of constipation, including chronic constipation, as directed by your doctor. It works over a period of about 24 to 48 hours. The liquid reaches your intestines virtually unchanged. Once there, the bacteria in your bowel split lactulose into its active parts. The active parts increase the action of your bowel and keep water in your bowel so that stools are moved through and are easier to pass.

Lactulose is also used to treat encephalopathy, a disorder of the brain causing confusion or mental problems as a result of liver disease or liver failure.

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.

For the treatment of constipation, the usual starting dose is 15 mL to 30 mL once daily. This dose may be increased to a maximum of 60 mL once daily. Remember that lactulose takes 24 to 48 hours for results in most cases. This product should not be used if it has only been a day or two since your last bowel movement. Laxatives should not be used for more than one week unless your doctor advises otherwise. If you are still bothered by constipation after one week of using this product, call your doctor.

For the treatment of encephalopathy, the usual adult dose is 30 mL to 45 mL taken 3 or 4 times daily. The dose in infants ranges from 2.5 mL to 10 mL daily in divided doses. The dose in children ranges from 40 mL to 90 mL daily in divided doses. After 1 to 2 days the dose may be adjusted to an amount required to result in 2 or 3 soft stools daily. In infants and children, if the starting dose results in diarrhea or if the diarrhea persists, contact your doctor.

Many things can affect the dose of medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

It is important to take this medication exactly as suggested by your doctor or pharmacist. If you miss a dose, take it as soon as possible and continue with your regular schedule. If it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Store this medication at room temperature, protect it from moisture, and keep it out of the reach of children.

Each mL of colourless to yellow, orange-flavoured syrup contains 667 mg of lactulose. Nonmedicinal ingredients: natural orange flavour, galactose, lactose, fructose and epilactose. Available in bottles of 15 mL, 30 mL, 250 mL, 500 mL and 1 L.

Do not take lactulose if you:

• are allergic to lactulose or any ingredients of the medication
• require a low galactose diet

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

• abdominal cramps
• diarrhea
• flatulence
• nausea

Although most of these side effects listed below don't happen very often, they could lead to serious problems if you do not seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

• worsening abdominal pain

Stop taking the medication and seek immediate medical attention if any of the following occur:

• signs of a serious allergic reaction (i.e., swelling of face or throat, hives, or difficulty breathing)

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.

Diabetes: People with diabetes may experience loss of glucose control when they use lactulose. If you have diabetes, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Signs and symptoms: This medication should not be used in the presence of abdominal pain, nausea, fever, or vomiting.

Pregnancy: This medication should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking this medication, contact your doctor immediately.

Breast-feeding: It is not known if lactulose passes into breast milk. If you are a breast-feeding mother and are taking this medication, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.

Children: Infants and children receiving this medication are at risk of dehydration.

Seniors: People over the age of 65 years may be more at risk of dehydration and changes in electrolytes from this medication.

There may be an interaction between lactulose and any of the following:

• aluminum hydroxide
• magnesium hydroxide
• other laxatives

If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

• stop taking one of the medications,
• change one of the medications to another,
• change how you are taking one or both of the medications, or
• leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than those listed above may interact with this medication. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.