Patient leaflet - Zeffix 100 mg film-coated tablets
1 What Zeffix is and what it is used for
The active ingredient in Zeffix is lamivudine. Zeffix is used to treat long term (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 analogue reverse transcriptase inhibitors (NRTIs).
Hepatitis B is a virus which infects the liver, causes long term (chronic) infection, and can lead to liver damage. Zeffix can be used in people whose liver is damaged, but still functions normally (compensated liver disease) and in combination with other medicines in people whose liver is damaged and does not function normally (decompensated liver disease).
Treatment with Zeffix can reduce the amount of hepatitis B virus in your body. This should lead to a reduction in liver damage and an improvement in your liver function. Not everyone responds to treatment with Zeffix in the same way. Your doctor will monitor the effectiveness of your treatment with regular blood tests.
2 What you need to know before you take Zeffix
Your healthcare provider should offer you counselling and testing for HIV infection before you start treatment with lamivudine for hepatitis B infection and during treatment. If you have or get HIV infection, see section 3.
Do not take Zeffix
if you’re allergic to lamivudine or to any of the other ingredients of this medicine (listed in Section 6). ➔ Check with your doctor if you think this
applies to you.
Warnings and precautions
Some people taking Zeffix or other similar medicines are more at risk of serious side effects. You need to be aware of the extra risks:
- if you have ever had other types of liver disease, such as hepatitis C
- if you’re seriously overweight (especially if you’re a woman).
➔ Talk to your doctor if any of these apply to
you. You may need extra check-ups, including blood tests, while you’re taking your medication. See Section 4 for more information about the risks. Don’t stop taking Zeffix without your doctor’s advice, as there is a risk of your hepatitis getting worse. When you stop taking Zeffix your doctor will monitor you for at least four months to check for any problems. This will mean taking blood samples to check for any raised liver enzyme levels, which may indicate liver damage. See section 3 for more information about how to take Zeffix.
Protect other people
Hepatitis B infection is spread by sexual contact with someone who has the infection, or by transfer of infected blood (for example, by sharing injection needles). Zeffix will not stop you passing hepatitis B infection on to other people. To protect other people from becoming infected with hepatitis B:
- Use a condom when you have oral or penetrative sex.
Don’t risk blood transfer - for example, don’t share needles.
Other medicines and Zeffix
Tell your doctor or pharmacist if you’re taking, have recently taken or might take any other medicines, including herbal medicines or other medicines you bought without a prescription.
Remember to tell your doctor or pharmacist if you begin taking a new medicine while you’re taking Zeffix. These medicines should not be used with Zeffix:
- medicines (usually liquids) containing sorbitol and other sugar alcohols (such as xylitol, mannitol, lactitol or maltitol), if taken regularly
- other medicines containing lamivudine, used to treat HIV infection (sometimes called the AIDS virus)
- emtricitabine used to treat HIV or hepatitis B infection
cladribine, used to treat hairy cell leukaemia ➔ Tell your doctor if you’re being treated with
any of these.
Pregnancy
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 with Zeffix without your doctor’s advice.
Breast-feeding
Zeffix can pass into breast-milk. If you are breast-feeding, or thinking about breast-feeding: ➔ Talk to your doctor before you take Zeffix. Driving and using machines
Zeffix may make you feel tired, which could affect your ability to drive or use machines.
➔ Don’t drive or use machines unless you are sure
you’re not affected.
Zeffix contains sodium
This medicine contains less than 1 mmol sodium (23 mg) per tablet, that is to say essentially ‘sodium-free’.
3 How to take Zeffix
Always take this medicine exactly as your doctor has told you to. Check with your doctor or pharmacist if you’re not sure.
Stay in regular contact with your doctor
Zeffix helps to control your hepatitis B infection. You need to keep taking it every day to control your infection and stop your illness getting worse. ➔ Keep in touch with your doctor, and don’t
stop taking Zeffix without your doctor’s advice. How much to take
The usual dose of Zeffix is one tablet (100 mg lamivudine) once a day.
Your doctor may prescribe a lower dose if you have problems with your kidneys. An oral solution of Zeffix is available for people who need a lower than usual dose, or who can’t take tablets.
➔ Talk to your doctor if this applies to you. Patients who also have or may get HIV infection
If you have or get HIV that is not being treated with medicines while taking lamivudine for the treatment of hepatitis B infection, the HIV virus may develop resistance to certain HIV medicines and become harder to treat. Lamivudine can also be used to treat HIV infection. Talk to your doctor if you have HIV infection. Your doctor may treat you with another medicine that contains a higher dose of lamivudine, usually 150 mg twice a day, as the lower dose of 100 mg lamivudine is
not enough to treat HIV infection. If you are planning to change your HIV treatment, discuss this change with your doctor first.
➔ Talk to your doctor if this applies to you. Swallow the tablet whole, with some water. Zeffix can be taken with or without food.
If you take more Zeffix than you should
If you accidentally take too much Zeffix, tell your doctor or your pharmacist, or contact your nearest hospital emergency department for further advice. If possible, show them the Zeffix pack.
If you forget to take Zeffix
If you forget to take a dose, take it as soon as you remember. Then continue your treatment as before. Don’t take a double dose to make up for a missed dose.
Don’t stop taking Zeffix
You must not stop taking Zeffix without consulting your doctor. There is a risk of your hepatitis getting worse (see section 2). When you stop taking Zeffix your doctor will monitor you for at least four months to check for any problems. This will mean taking blood samples to check for any raised liver enzyme levels, which may indicate liver damage.
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4 Possible side effects
Like all medicines, this medicine can cause side effects, although not everybody gets them. Side effects that were commonly reported in Zeffix clinical trials were tiredness, respiratory tract infections, throat discomfort, headache, stomach discomfort and pain, nausea, vomiting and diarrhoea, increases in liver enzymes and enzymes produced in the muscles (see below).
Allergic reaction
These are rare (may affect up to 1 in 1,000 people). Signs include:
- swelling of eyelids, face or lips
- difficulty swallowing or breathing
➔ Contact a doctor immediately if you get these
symptoms. Stop taking Zeffix.
Side effects thought to be caused by Zeffix
A very common side effect (these may affect more than 1 in 10 people) which may show up in blood tests is:
- an increase in the level of some liver enzymes (transaminases), which may be a sign of inflammation or damage in the liver. A common side effect (these may affect up to 1 in 10 people) is:
- cramps and muscle pains
- skin rash or ‘hives’ anywhere on the body A common side effect which may show up in blood tests is:
an increase in the level of an enzyme produced in the muscles (creatine phosphokinase) which may be a sign that body tissue is damaged.
A very rare side effect (these may affect up to 1 in 10,000 people) is:
- lactic acidosis (excess lactic acid in the blood).
Other side effects
Other side effects have occurred in a very small number of people but their exact frequency is unknown
- breakdown of muscle tissue
- a worsening of liver disease after Zeffix is stopped or during treatment if the hepatitis B virus becomes resistant to Zeffix. This can be fatal in some people.
A side effect which may show up in blood tests is:
- a decrease in the number of cells involved in blood clotting (thrombocytopenia).
If you get any side effects
➔ Talk to your doctor or pharmacist. This
includes any possible side effects not listed in this leaflet.
Reporting of side effects
If you get any side effects, talk to your doctor or pharmacist. This includes any possible side effects not listed in this leaflet. You can also report side effects directly via Yellow Card Scheme Website: www.mhra.gov.uk/yellowcard or search for MHRA Yellow Card in the Google Play or Apple App Store. By reporting side effects you can help provide more information on the safety of this medicine.
5 How to store Zeffix
Keep this medicine out of the sight and reach of children.
Don’t take this medicine after the expiry date shown on the carton and blister.
Don’t store above 30 °C.
Do not throw away any medicines in your wastewater or household rubbish. Ask your pharmacist how to throw away medicines you no longer use. These measures will help to protect the environment.
6 Contents of the pack and other information
What Zeffix contains
The active substance is lamivudine. Each film-coated tablet contains 100 mg of lamivudine.
The other ingredients are: microcrystalline cellulose, sodium starch glycolate, magnesium stearate, hypromellose, titanium dioxide, macrogol 400, polysorbate 80, synthetic yellow and red iron oxide.
What Zeffix looks like and contents of the pack
Zeffix film-coated tablets are supplied in tamper evident foil blisters containing 28 or 84 tablets. The tablets are butterscotch coloured, capsule shaped, biconvex and engraved “GX CG5” on one side. Not all pack-sizes may be available in your country.
Manufacturer
Delpharm Poznań Spółka Akcyjna
ul. Grunwaldzka 189, 60-322 Poznan, Poland Marketing Authorisation Holder
GlaxoSmithKline UK Limited
79 New Oxford Street
London
WC1A 1DG
United Kingdom
This leaflet was last revised in March 2025
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Production Site:
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Leaflet - flat dimensions (width x height):
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folded dimensions (width x height): 148 x 36 mm
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random repeats:
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Carton - dimensions (width x height x depth):
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Point of Sale Code Number:
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NOTE TO MARKET Local approvers must ensure that trade mark and copyright statements included in the brief comply with guidance provided by
Manufacturing Site Number:
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Product Market Trade Name:
ZEFFIX
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Additional Info (1):
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200 mm Measuring Bar Artwork copyright is the property of the GSK Group of Companies. All suppliers providing a service to GSK for printed components of any description must ensure that they have a licence for all fonts / software used in conjunction with GSK artwork. The distribution and use of fonts / software without a licence constitutes an intellectual property infringement. GSK will not accept any liability for the breach of third party intellectual property rights by printed component suppliers. The GSK certification / audit process requires suppliers to declare that they do not use unlicensed fonts / software and may require the supplier to produce evidence of such licence to GSK.