Zeffix – Lamivudine uses, dose and side effects


100 mg film-coated tablets
of lamivudine

What Zeffix is ​​and what it is used for

The active substance in Zeffix is ​​lamivudine.

Zeffix is ​​used to treat chronic hepatitis B infection in adults.

Zeffix is ​​an antiviral medicine that suppresses the hepatitis B virus and belongs to a group of medicines called nucleoside analog reverse transcriptase inhibitors (NRTIs).

Hepatitis B is a virus that infects the liver, causes long-term ( chronic ) infections, and can cause damage to the liver. Zeffix can be used by people whose liver is damaged but still functioning normally (compensated liver disease) and in combination with other medicines by people whose liver is damaged and not functioning normally (decompensated liver disease).

Treatment with Zeffix can reduce the amount of hepatitis B virus in the body. In this way, damage to the liver can be reduced and liver function can be improved. Not everyone responds to treatment with Zeffix in the same way. Your doctor will monitor the effectiveness of your treatment by regularly taking blood samples.

What you need to know before taking Zeffix

Do not use Zeffix

  • if you are allergic to lamivudine or any other ingredient in this medicine ( listed in section 6 ).
  • Consult your doctor if you think this applies to you.

Warnings and precautions

Some people who take Zeffix or other similar medicines are at greater risk of serious side effects. You need to be aware of the additional risks:

  • if you have ever had other types of liver disease, such as hepatitis C
  • if you are severely overweight (especially if you are a woman)
  • Talk to your doctor if any of these apply to you. You may need extra checks, including blood tests, while you are taking the medicine. See section 4 for more information on the risks.

Do not stop taking Zeffix without first talking to your doctor, as there is a risk that your hepatitis will get worse. After you stop taking Zeffix, your doctor will check you for at least four months to rule out any problems. This means that blood samples will be taken to check if you have elevated levels of liver enzymes, which can be signs of liver damage. See section 3 for more information on how to take Zeffix.

Protect other people

Hepatitis B infection is spread through sexual contact with someone who has the infection or through the transfer of infected blood (for example, by sharing hypodermic needles). Zeffix does not prevent you from passing hepatitis B infection on to other people. To protect others from becoming infected with hepatitis B:

  • Use a condom when having oral or penetrative sex.
  • Do not risk transmission via blood – for example, do not share injection needles with others.

Other medicines and Zeffix

Tell your doctor or pharmacist if you are taking, have recently taken, or might take any other medicines, including herbal and non-prescription medicines.

Remember to tell your doctor or pharmacist if you start taking any new medicines while taking Zeffix.

These medicines should not be taken with Zeffix:

  • medicines (usual liquids) containing sorbitol and other sugar alcohols (such as xylitol, mannitol, lactitol, and maltitol), if taken regularly
  • other medicines containing lamivudine used to treat HIV infection ( sometimes called the AIDS virus )
  • emtricitabine, which is used to treat HIV or hepatitis B infection
  • cladribine, which is used to treat hairy cell leukemia.
  • Tell your doctor if you are being treated with any of these medicines.

Pregnancy and breastfeeding


If you are pregnant, think you may be pregnant, or are planning to have a baby:

  • Talk to your doctor about the risks and benefits of taking Zeffix during your pregnancy. Do not stop treatment without first consulting your doctor.


Zeffix can pass into breast milk. If you are breastfeeding or thinking about breastfeeding:

  • Talk to your doctor before taking Zeffix.

Driving ability and use of machinery

Zeffix can make you feel tired which may affect your ability to drive or use machines.

  • Do not drive or operate machinery unless you are sure that your abilities are unaffected.

Zeffix contains sodium

This medicine contains less than 1 mmol (23 mg) of sodium per tablet, i.e. it is almost “sodium-free”.

How to take Zeffix

Always take this medicine as directed by your doctor. Ask your doctor or pharmacist if you are unsure.

Have regular contact with your doctor

Zeffix helps you control your hepatitis B infection. You must continue to take it every day to control your infection and prevent your illness from getting worse.

  • Keep in touch with your doctor and do not stop taking Zeffix without first consulting your doctor.

How much to take

The usual dose of Zeffix is ​​one tablet (100 mg lamivudine) once daily.

Your doctor may prescribe a lower dose if you have kidney problems. There is an oral solution of Zeffix available for people who need a lower dose or who cannot swallow tablets.

  • Talk to your doctor if this applies to you.

If you are already taking another medicine for HIV – infection that contains lamivudine, your doctor will continue to treat you with the higher dose (usually 150 mg twice daily), because dose one of lamivudine in Zeffix (100 mg) is not enough to treat HIV infection. If you plan to change your HIV treatment, discuss this change with your doctor first.

Swallow the tablet whole with water. Zeffix can be taken with or without food.

If you have taken too much Zeffix

If you accidentally take too much Zeffix, contact your doctor, pharmacist, or the emergency department of your nearest hospital for further advice.

Show the Zeffix packaging if possible.

If you forget to take Zeffix

If you have forgotten to take a dose, take it as soon as possible. Then continue the treatment as prescribed. Do not take a double dose to make up for a missed dose.

Do not stop taking Zeffix

You should not stop taking Zeffix without consulting your doctor first. There is a risk that your hepatitis will get worse ( see section 2 ). After you stop taking Zeffix, your doctor will check you for at least four months to rule out any problems. This means that blood samples will be taken to check if you have elevated levels of liver enzymes, which can be signs of liver damage.

Possible side effects

Like all medicines, this medicine can cause side effects, although not everybody gets them.

Side effects commonly reported in clinical studies with Zeffix were fatigue, respiratory tract infections, sore throat, headache, pain, and discomfort from the stomach, nausea, vomiting, and diarrhea, and elevation of liver enzymes and enzymes produced in the muscles ( see below ).

Allergic reaction

This is rare (may affect up to 1 in 1000 users). Signs include:

  • swelling of the eyelids, face, or lips
  • difficulty swallowing or breathing
  • Contact a doctor immediately if you experience any of these symptoms. Stop taking Zeffix.

Side effects that are assumed to be due to Zeffix

A very common side effect (which may affect more than 1 in 10 people) that can be detected in blood tests is:

  • an increase in the level of certain liver enzymes ( transaminases ), which may be a sign of inflammation or damage to the liver.

A common side effect (which may affect up to 1 in 10 users) is:

  • cramps and muscle pain
  • skin rash or hives on the body.

A common side effect that can be detected in blood tests is:

  • an increase in the level of an enzyme produced in the muscles ( creatinine phosphokinase ) which can be a sign that body tissue is damaged.

A very rare side effect (which may affect up to 1 in 10,000 users) is:

  • Lactic acidosis (excess of lactic acid in the blood).

Other side effects are

Other side effects have occurred in a very small number of users but the exact frequency is unknown.

  • breakdown of muscle tissue
  • a worsening of liver disease after stopping treatment with Zeffix or during treatment if the hepatitis B virus et develops resistance to Zeffix. This can be fatal for some people

A side effect that can be detected in blood tests is:

  • a reduction in the number of cells involved in blood clotting ( thrombocytopenia ).

If you get any side effects are

  • Talk to your doctor or pharmacist. This also applies to any side effects that are not mentioned in this information.

How to store Zeffix

Keep this medicine out of the sight and reach of children.

Use before the expiry date stated on the carton and blister.

Store at a maximum of 30 °C.

Medicines must not be thrown into the drain or among the household waste. Ask the pharmacist how to dispose of medicines that are no longer used. These measures will help to protect the environment.

Contents of the packaging and other information

Contents declaration

The active substance is lamivudine. Each film-coated tablet contains 100 mg of lamivudine.

Other ingredients are microcrystalline cellulose, sodium starch glycolate, magnesium stearate, hypromellose, titanium dioxide, macrogol 400, polysorbate 80, and synthetic yellow, and red iron oxide.

Appearance and package sizes of the medicine

Zeffix film-coated tablets are supplied in warranty-sealed blisters of 28 or 84 tablets. The tablets are brown-yellow, capsule-shaped, biconvex, and marked “GX CG5” on one side.

Not all pack sizes may be marketed.

Marketing authorization holder and manufacturer

ManufacturerMarketing Authorisation Holder
Delpharm Poznań Spółka Akcyjnaul. Grunwaldzka 18960-322 Poznan

GlaxoSmithKline (Ireland) Limited12 RiverwalkCitywest Business CampusDublin 24Ireland

Contact the representative of the Marketing Authorization Holder if you would like to know more about this medicine:

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