Combivir (Zidovudine, lamivudine)

How does it work?

Combivir tablets contain two active ingredients, zidovudine (also known as azidothymidine or AZT) and lamivudine (also known as 3TC). These are both medicines called nucleoside reverse transcriptase inhibitors. They are used in the treatment of HIV (human immunodeficiency virus) infection.

AIDS (acquired immune deficiency syndrome) is caused by infection with HIV. This virus invades cells of the immune system, particularly the white blood cells known as CD4 T-helper lymphocytes. These cells normally work to activate other cells in the immune system to fight infection. Since HIV kills CD4 T-helper cells, over time the body becomes less able to fight the virus or subsequent infections.

Once the virus is inside the CD4 T-cell it multiplies. Part of the process of viral multiplication involves the conversion of the virus genetic material, RNA, into DNA. This is achieved by a compound essential to the virus, called reverse transcriptase. Reverse transcriptase is a compound known as an enzyme. Zidovudine and lamivudine work by blocking the action of this enzyme, thereby interfering with the conversion of viral RNA into DNA. This stops the virus from multiplying.

There is no cure for HIV, but zidovudine and lamivudine are two of a number of medications that lower the amount of virus in the body (viral load) and slow the progression of the disease from HIV to AIDS. A combination of several anti-HIV medicines is required to fight the infection because the virus can become resistant to one agent very quickly. Zidovudine and lamivudine are used together to help prevent resistance occurring. This combination preparation reduces the number of tablets to be taken and therefore simplifies treatment.

What is it used for?

  • HIV infection.


  • The HIV virus is very good at becoming resistant to anti-HIV medicines. For this reason it is very important that you carefully follow your doctor's instructions for taking your anti-HIV medicines, in order to maintain effective levels of the medicines in your blood. If the blood levels drop, the virus will be given more chance to replicate and develop resistance to the drugs. Skipping even a few doses increases the risk of treatment failure, so you should try to ensure that you take all your doses at the correct time, and that you visit your doctor for repeat prescriptions before you run out.
  • Treatment of HIV infection with anti-HIV medicines such as this one does not reduce the risk of transmitting the virus to other people through sexual contact or blood contamination. You should continue to use condoms to prevent transmitting the virus to your sexual partner.
  • Combination antiretroviral therapy has been associated with a redistribution of body fat (lipodystrophy) in people with HIV. The long-term consequences of this are currently unknown, however your doctor may wish to monitor your body fat, and the levels of lipids (eg cholesterol) and sugar (glucose) in your blood, and may prescribe additional medicines for any lipid disorders that occur during treatment with this medicine. Contact your doctor if you notice any changes in your body fat during treatment with your HIV medicines.
  • Some people being treated with combination antiretroviral therapy may develop a bone condition called osteonecrosis. This condition is caused by loss of blood supply to a bone, causing death of the bone tissue. The risk of the condition is thought to be increased by corticosteroid use, alcohol consumption, severe immunosuppression, higher body mass index, advanced HIV disease and long-term use of antiretroviral medicines. If you notice any joint stiffness, aches and pains (especially of the hip, knee and shoulder) or difficulty in movement while using this medicine, you should tell your doctor so this can be investigated.
  • You should have regular blood tests to monitor your liver function while you are taking this medicine. This is especially important if you already have any problems with your liver, in particular chronic hepatitis B or C. Symptoms that may suggest a liver problem include persistent nausea and vomiting, abdominal pain, or the development of jaundice (a yellow colouring to the skin and the whites of the eyes). Consult your doctor if you experience any of these symptoms.
  • If you suffer from chronic hepatitis B you should not stop taking this medicine without instructions from your doctor, as this may cause a recurrence of your hepatitis.
  • The class of medicines that lamivudine and zidovudine belong to can cause a rare but serious condition called lactic acidosis, which is an excess of lactic acid in the blood, together with an enlarged liver. This side effect is more likely to occur in overweight women and people with liver disease (particularly hepatitis C treated with alpha interferon and ribavirin). If it occurs, lactic acidosis usually develops after a few months of treatment. Your doctor will monitor you for this side effect, but symptoms that might indicate it's development include rapid and/or deep breathing and non-specific symptoms such as feeling weak, sick or generally unwell, vomiting, abdominal pain, loss of appetite or weight loss. You should tell your doctor if you experience any of these.
  • Your doctor may also want you to have regular blood tests during treatment to check for a side effect called pancreatitis (inflammation of the pancreas). You should let your doctor know if you experience sudden unexplained stomach or abdominal pain, nausea or vomiting while taking this medicine, as these could be symptoms of pancreatitis.
  • While taking this medicine you should also have regular blood tests to allow your doctor to monitor the number of blood cells in your blood. This is because zidovudine can sometimes cause a decrease in the numbers of white blood cells and red blood cells in the blood.

Use with caution in

  • Elderly people.
  • Decreased kidney function.
  • Decreased liver function.
  • Enlarged liver (hepatomegaly).
  • Liver disease.
  • Hepatitis, especially chronic hepatitis B or C.
  • History of alcohol abuse.
  • Obese women.
  • Vitamin B12 deficiency.

Not to be used in

  • Children weighing less than 14kg.
  • People with abnormally low levels of haemoglobin in their blood.
  • People with abnormally low levels of a type of white blood cell called a neutrophil in their blood.

This medicine should not be used if you are allergic to one or any of its ingredients. Please inform your doctor or pharmacist if you have previously experienced such an allergy.If you feel you have experienced an allergic reaction, stop using this medicine and inform your doctor or pharmacist immediately.

Pregnancy and breastfeeding

Certain medicines should not be used during pregnancy or breastfeeding. However, other medicines may be safely used in pregnancy or breastfeeding providing the benefits to the mother outweigh the risks to the unborn baby. Always inform your doctor if you are pregnant or planning a pregnancy, before using any medicine.

  • The safety of this medicine in pregnancy has not been established. It should only be used during pregnancy, particularly in the first trimester, if the expected benefit to the mother outweighs any potential risk to the developing foetus. Seek medical advice from your doctor.
  • It is recommended that women infected with the HIV virus must not breastfeed their infants under any circumstances, in order to avoid transmission of the virus to the baby. Seek medical advice from your doctor.

Side effects

Medicines and their possible side effects can affect individual people in different ways. The following are some of the side effects that are known to be associated with this medicine. Just because a side effect is stated here does not mean that all people using this medicine will experience that or any side effect.

  • Headache.
  • Difficulty in sleeping (insomnia).
  • Fatigue.
  • Disturbances of the gut such as diarrhoea, nausea, vomiting or abdominal pain.
  • Cough.
  • Hair loss (alopecia).
  • Rash or itching.
  • Pain in the muscles and joints.
  • Weakness or loss of strength (asthenia).
  • Fever.
  • General feeling of being unwell (malaise).
  • Dizziness.
  • Decrease in the number of a type of white blood cell (neutrophil) in the blood (neutropenia).
  • Low red blood cell count (anaemia).
  • Pins and needles (paraesthesia).
  • Anxiety and depression.
  • Inflammation of the pancreas (pancreatitis).
  • Elevated levels of lactic acid in the blood (lactic acidosis).
  • Liver disorders.

The side effects listed above may not include all of the side effects reported by the drug's manufacturer.For more information about any other possible risks associated with this medicine, please read the information provided with the medicine or consult your doctor or pharmacist.

How can this medicine affect other medicines?

It is important to tell your doctor or pharmacist what medicines you are already taking, including those bought without a prescription and herbal medicines, before you start treatment with this medicine. Similarly, check with your doctor or pharmacist before taking any new medicines while taking this one, to ensure that the combination is safe.

The manufacturer recommends that Combivir is not used in combination with the following medicines:

  • stavudine (zidovudine may inhibit effect of stavudine)
  • ribavirin (ribavirin may inhibit effect of zidovudine)
  • ganciclovir
  • foscarnet
  • zalcitabine.

Rifampicin may decrease the blood level of zidovudine and could therefore make it less effective.

The following medicines may increase the blood level of zidovudine and may therefore increase the risk of its side effects:

  • atovaquone
  • benzodiazepines, eg oxazepam, lorazepam
  • fluconazole
  • methadone
  • probenecid
  • sodium valproate or valproic acid.

There may be an increased risk of blood or kidney disorders if zidovudine is used in combination any of the following medicines, which can also decrease blood cells and have side effects on the kidneys:

  • amphotericin
  • dapsone
  • doxorubicin
  • flucytosine
  • interferon
  • pentamidine
  • vinblastine
  • vincristine.

If your doctor decides you need treatment with any of these medicines while you are taking Combivir, extra care should be taken to monitor your kidney function and levels of blood cells.

Trimethoprim may increase the blood level of lamivudine. This should not require a dose adjustment unless you have kidney problems, however you should be well monitored by your doctor if you are prescribed trimethoprim or co-trimoxazole (which contains trimethoprim) while taking this medicine. The manufacturer recommends that high doses of co-trimoxazole for the treatment of Pneumocystis carinii pneumonia (PCP) and toxoplasmosis should be avoided in people taking Combivir.

Clarithromycin tablets can reduce the absorption of zidovudine from the gut. If you need to take clarithromycin to treat an infection, this problem can be avoided by separating your doses of Combivir and clarithromycin by at least two hours. For more advice ask your pharmacist.

Other medicines containing the same active ingredients

There are currently no other medicines available in the UK that contain this lamivudine and zidovudine combination.

Epivir contains just lamivudine.

Retrovir contains just zidovudine.

Trizivir contains lamivudine and zidovudine in combination with another anti-HIV medicine called abacavir.