Entecavir belongs to a group of medications called antivirals. It is used to treat people with chronic hepatitis B infection with evidence of active hepatitis B virus replication (reproduction) and evidence of liver damage. It works by stopping the hepatitis B virus from reproducing. There is no cure for hepatitis B infection. Entecavir can decrease the amount of hepatitis B virus in the body and may reduce the damage done to the liver by the hepatitis B virus.

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.

The usual recommended dose for adults and adolescents 16 years of age and older is 0.5 mg once daily. People who have experienced active disease while taking a similar medication called lamivudine may need to take 1 mg once daily. People with reduced kidney function may require a lower dose, as directed by their 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.

Entecavir should be taken on an empty stomach, at least 2 hours before a meal or 2 hours after a meal. The tablet should be swallowed whole with water.

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 light and moisture, and keep it out of the reach of children.

Each white, triangular, film-coated tablet, debossed "A" on one side and "88" on the other side, contains 0.5 mg of entecavir. Nonmedicinal ingredients: crospovidone, hypromellose, lactose monohydrate, macrogol, magnesium stearate, microcrystalline cellulose, polysorbate 80, and titanium dioxide.

Do not take entecavir if you are allergic to entecavir or any ingredients of the medication.

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.

• diarrhea
• dizziness
• drowsiness
• fatigue
• headache
• heartburn
• nausea
• trouble sleeping
• vomiting

Although most of the 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:

• rash
• signs of liver problems, e.g.:
• dark urine
• diarrhea
• loss of appetite
• nausea
• pale stools
• vomiting
• weight loss
• yellowing of the skin or whites of the eyes

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

• signs of a serious allergic reaction:
• difficulty breathing
• hives
• swelling of the face, lips, eyes, or throat
• symptoms of lactic acidosis:
• abdominal pain
• coldness of arms and legs
• dizziness
• nausea
• shortness of breath
• unusual muscle pain
• vomiting
• weakness

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.

Hepatitis B transmission: Treatment with entecavir does not reduce the risk of passing on hepatitis B to other people through sexual contact and blood transfer. You should continue to take measures to prevent giving hepatitis B to other people (e.g., using condoms) while taking this medication.

Human immunodeficiency virus (HIV): People with HIV infection should discuss with their doctor how this medication may affect their medical condition. If you are taking entecavir for chronic hepatitis B and are not taking any medications for HIV at the same time, some HIV medications that you take in the future may not work as well to treat HIV. Entecavir has not been studied for the treatment of HIV. Your doctor may test you for HIV before beginning treatment with entecavir. If you think that you might have HIV, contact your doctor immediately to get tested.

Kidney function: This medication is removed from the body by the kidneys. If the kidneys are not working properly, entecavir may build up in the body and cause side effects. People with reduced kidney function may need a different dose of the medication. If you have decreased kidney function or kidney disease, 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.

Lactic acidosis and enlarged liver: Entecavir can cause a rare but serious condition called lactic acidosis (buildup of lactic acid in the blood) together with an enlarged liver and fat in the liver. If you experience any of the following symptoms, call your doctor immediately:

• abdominal pain, swelling, or bloating
• dark-coloured urine
• diarrhea
• fatigue
• feeling unwell
• light-coloured stools
• loss of appetite for several days
• nausea
• shortness of breath
• vomiting
• weakness
• weight loss
• yellow skin or whites of eyes

Your doctor will periodically monitor you and perform laboratory tests to check your liver function.

Lactose intolerance: Entecavir tablets contain lactose. If you have been told that you are intolerant to lactose, contact your doctor before taking this medication.

Liver transplant: The safety and effectiveness of entecavir has not been tested in people who have had a liver transplant. It is not known if entecavir will interact with anti-rejection medications (i.e., cyclosporine, tacrolimus) commonly used after an organ transplant. If you have had a liver transplant, 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.

Stopping the medication: If you stop taking entecavir, your hepatitis B infection could get worse. Take the medication exactly as prescribed by your doctor, and do not stop taking the medication without checking with your doctor first.

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 entecavir 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: The safety and effectiveness of using this medication have not been established for children less than 16 years of age.

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

• cladribine
• orlistat

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.