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Update Date 08/05/2020 . 5 mins read
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What is Zeffix® (Lamivudine) used for?

Zeffix® is commonly used to treat patients, who are 2 years of age or over with long term (chronic) viral infection of the liver caused by hepatitis B. It has not been shown to reduce the risk of passing hepatitis B to others.

Zeffix® may be prescribed for other uses; ask your doctor or pharmacist for more information.

How should I take Zeffix® (Lamivudine)?

Zeffix® tablets should be swallowed whole with a glass of water, and can be taken with or without food.

In order for Zeffix® tablets to be effective, you must take Zeffix® tablets every day for as long as your doctor says you should take them.

Ask your health care provider any questions you may have about how to use Zeffix®.

How do I store Zeffix® (Lamivudine)?

Zeffix® is best stored at room temperature away from direct light and moisture. To prevent drug damage, you should not store Zeffix® in the bathroom or the freezer. There may be different brands of Zeffix® that may have different storage needs. It is important to always check the product package for instructions on storage, or ask your pharmacist. For safety, you should keep all medicines away from children and pets.

You should not flush Zeffix® down the toilet or pour them into a drain unless instructed to do so. It is important to properly discard this product when it is expired or no longer needed. Consult your pharmacist for more details about how to safely discard your product.

Precautions & warnings

What should I know before using Zeffix® (Lamivudine)?

Consult with your doctor or pharmacist, if:

  • You are pregnant or breastfeeding. This is because, while you are expecting or feeding a baby, you should only take medicines on the recommendation of a doctor.
  • You are taking any other medicines. This includes any medicines you are taking which are available to buy without a prescription, such as herbal and complementary medicines.
  • You have allergy with any of active or inactive ingredients of Zeffix® or other medications.
  • You have any other illnesses, disorders, or medical conditions, such as liver problems or kidney problems.
  • You have any other types of allergies, such as to foods, dyes, preservatives, or animals.

Is it safe during pregnancy or breastfeeding?


There are no adequate studies in women for determining risk when using this medication during pregnancy or while breastfeeding. Please always consult with your doctor to weigh the potential benefits and risks before taking this medication. This medication is pregnancy risk category C, according to the US Food and Drug Administration (FDA).

FDA pregnancy risk category reference below:

  • A=No risk
  • B=No risk in some studies
  • C=There may be some risk
  • D=Positive evidence of risk
  • X=Contraindicated
  • N=Unknown


Zeffix® should only be used in a nursing mother if the expected benefit justifies the potential risk to the infant. A decision must be made whether to discontinue breastfeeding or to discontinue/abstain from Zeffix® therapy, taking into account the benefit of breastfeeding for the child and the benefit of therapy for the woman.

Always consult your health care provider prior to using this medication if you are pregnant, breastfeeding.

Side effects

What side effects can occur from Zeffix® (Lamivudine)?

Here are common side effects:

  • Headache
  • Vomiting
  • Diarrhea
  • Nausea
  • Fatigue/tiredness
  • Abdominal discomfort and pain
  • Coughing, with phlegm, not associated with a cold or flu
  • Dizziness
  • Abnormal Liver function tests
  • Muscle disorders (including muscle pain and cramps)

Tell your doctor immediately if you notice any of the following:

  • Wheezing
  • Swelling of the lips/mouth
  • Difficulty in breathing
  • Hay fever
  • Lumpy rash (hives)
  • Fainting

Not everyone experiences these side effects. There may be some side effects not listed above. If you have any concerns about a side-effect, please consult your doctor or pharmacist.


What drugs may interact with Zeffix® (Lamivudine)?

Zeffix® may interact with other drugs that you are currently taking, which can change how your drug works or increase your risk for serious side effects. To avoid any potential drug interactions, you should keep a list of all the drugs you are using (including prescription drugs, nonprescription drugs, and herbal products) and share it with your doctor and pharmacist. For your safety, do not start, stop, or change the dosage of any drugs without your doctor’s approval.

Here are some medications may interact with Zeffix®, such as:

  • Trimethoprim
  • Sulphamethoxazole
  • Immunosuppressant medicines (e.g. Cyclosporin)
  • Zalcitabine
  • Emtricitabine

Does food or alcohol interact with Zeffix® (Lamivudine)?

Zeffix® may interact with food or alcohol by altering the way the drug works or increase the risk for serious side effects. Please discuss with your doctor or pharmacist any potential food or alcohol interactions before using this drug.

What health conditions may interact with Zeffix® (Lamivudine)?

Zeffix® may interact with your health condition. This interaction may worsen your health condition or alter the way the drug works. It is important to always let your doctor and pharmacist know all the health conditions you currently have, especially:

  • Kidney problems
  • Problems with your pancreas


The information provided is not a substitute for any medical advice. You should ALWAYS consult with your doctor or pharmacist before using this medication.

What is the dose of Zeffix® (Lamivudine) for an adult?

  • Dose: 100 mg tablet once a day. Your doctor may prescribe a different dosage.
  • Each patient responds to the treatment differently. Your doctor will check you by taking regular blood samples. The results will help decide when you should stop taking Zeffix®.

What is the dose of Zeffix® (Lamivudine) for a child?

Children from two to eleven years:

  • The recommended dose is 3mg/kg once daily up to a maximum of 100mg daily.
  • Treatment in this patient population should not be extended beyond one year’s duration.

Children less than two years:

There are insufficient data available to propose specific dosage recommendations in this age group.

How is Zeffix® (Lamivudine) available?

Zeffix® is available in the following dosage forms and strengths:

  • Zeffix® film-coated tablets: 100 mg lamivudine.

What should I do in case of an emergency or overdose?

In case of an emergency or an overdose, call your local emergency services or go to your nearest emergency room.

It is also important to carry a written list of all of the prescription and nonprescription (over-the-counter) medicines you are taking with you in case of emergencies.

What should I do if I miss a dose?

If you miss a dose of Zeffix®, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and take your regular dose as scheduled. Do not take a double dose.


Zeffix® (Lamivudine). http://reference.medscape.com/drug/epivir-hbv-lamivudine-342621#6. Accessed November 10, 2016

Zeffix® (Lamivudine). http://www.medsafe.govt.nz/profs/datasheet/z/Zeffixtab.pdf. Accessed November 10, 2016

Hello Health Group does not provide medical advice, diagnosis or treatment.

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