Entecavir to prevent hepatitis B returning

This information is for people who have been tested for the hepatitis B virus (HBV) and the results show that you have had the infection in the past.

HBV is an infection that affects the liver and is carried through the body in your blood and body fluids. 

Usually once the HBV infection has ended, the body develops immunity to protect it from the virus.  

For people who need treatment that suppresses the immune system, there is a risk the HBV infection may return. This is called HBV reactivation, and it can damage the liver. 

HBV reactivation can be prevented with antiviral medicine called entecavir. It works by stopping the virus from spreading in the liver and is very effective when taken regularly to prevent HBV reactivation and liver damage.

Before taking entecavir

We need to take blood tests to look for past HBV infection and to exclude other viral infections. 

Blood tests include:

  • full blood count
  • liver function 
  • kidney function

Tell us if you are pregnant or planning to be pregnant before starting entecavir.

How to take entecavir

Entecavir is a tablet taken once a day every day by mouth and can be taken with or without food.

How long you need to be on entecavir depends on your immune suppressive treatment plan. 

Once your immune suppressive treatment has finished you will need to continue taking entecavir for a while. 

If you need to have immune suppressive treatment permanently, then you will also need to take entecavir permanently. 

Your healthcare professional will tell you how long you need to continue taking entecavir. 

Regular blood tests

We take blood tests 1 month after starting entecavir.

After that, we will monitor you and take blood tests every 3 to 6 months. 

Tests include:

  • hepatitis B status
  • full blood count
  • liver function
  • kidney function

Monitoring blood tests are essential. If these are not done your prescription may be withheld until you have your blood test.

It is important that all medicines are kept out of the reach of children. 

Taking entecavir with other medicines

Entecavir can interact with other medicines.

Before you start taking entecavir, please let your doctor know about all the medicines you take. This should include anything prescribed for you and any medicines you buy from a shop or pharmacy (including herbal and homeopathic).

When you have started treatment, you should always check with your doctor or pharmacist before starting any new medicines. 

If you forget to take a dose

If you forget to take your entecavir at your usual time, take it as soon as you remember. 

If you do not remember until the next day, leave out the missed dose.

Do not double your dose if you have forgotten.

Pregnancy and breastfeeding

Do not take entecavir if you are pregnant.

Should you wish to plan a pregnancy while on entecavir this should be discussed carefully with your doctor first. 

It's important you tell us if you are pregnant or planning on getting pregnant so that we can review all of your medicines and monitor you more closely. We may suggest using an alternative medicine. 

If you need to, use 2 reliable forms of contraception while taking entecavir to minimise the risk of unintended pregnancy. 

Do not breastfeed while taking entecavir without first discussing with your doctor or medical team.

Drinking alcohol

We recommend you keep well within the national recommended limits of alcohol (maximum of 14 units per week).

14 units is about the same as 6 pints of average-strength beer or 10 small glasses of lower-strength wine.

Any amount of alcohol can damage the liver, especially if you have an underlying condition. Depending on the state of your liver, your clinician may ask you to avoid alcohol completely.

Side effects

Most people who take entecavir tolerate it well. More information on side effects can be found in the manufacturer’s patient information leaflet that comes with the medicine. 

Possible side effects include:

  • headache
  • dizziness
  • fatigue
  • trouble sleeping (insomnia)
  • feeling sick (nausea)
  • being sick (vomiting)
  • diarrhoea
  • indigestion
  • rash
  • hair loss (Alopecia) 
  • abnormal liver tests

The side effects may reduce over time but please talk to your doctor or nurse if you have any questions about them.

Contact your GP or a healthcare professional if:

you develop signs of an allergic reaction, including:

  • a rash 
  • swelling or breathing difficulties (signs of anaphylaxis) 

Repeat prescription

Entecavir can only be prescribed by a healthcare professional at the hospital. 

If you are running out of your supply you should contact the team that prescribes your immune suppressive treatment to arrange a further prescription. 

Resource number: 5355/VER1
Last reviewed: May 2023
Next review due: May 2026

Who to contact

If you have any questions or concerns about your treatment and condition, please contact the team who prescribes your immunosuppressive medicine.

Do you have any comments or concerns about your care?

Contact our Patient Advice and Liaison Service (PALS)

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