Abacavir, lamivudine, zidovudine (Trizivir)

How does it work?

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

AIDS (acquired immune deficiency syndrome) is caused by infection with HIV. The HIV 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, the body cannot 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, lamivudine and abacavir 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, lamivudine and abacavir are three of a number of medicines that lower the amount of virus in the body (viral load) and therefore slow down 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, lamivudine and abacavir are used together to prevent resistance occurring. This combination preparation reduces the number of tablets to be taken and therefore simplifies treatment. It is recommended that individuals are stabilised on the medicines separately for six to eight weeks before being transferred to this combination product.

What is it used for?

  • HIV infection.

Warning!

  • Abacavir may cause a severe allergic reaction in some people that may become life-threatening if treatment is not stopped. If it happens, this reaction usually occurs within 6 weeks of starting the medicine, but it may occur at any time. Symptoms of the allergic reaction generally include fever and/or a rash. Other frequent symptoms include feeling sick, vomiting, diarrhoea, abdominal pain, shortness of breath, cough, headache, aching muscles, severe tiredness or feeling generally unwell. Other possible symptoms include aching joints, sore throat, swollen glands, mouth ulcers, eye inflammation (conjunctivitis), pins and needles sensations and low blood pressure. If you get any of these symptoms during treatment you should contact your doctor IMMEDIATELY for advice on whether to stop taking this medicine.
  • Due to the risk of serious allergic reactions to this medicine you should be closely monitored by your doctor during treatment, particularly during the first two months of treatment, when you should be seen by your doctor every two weeks.
  • If you are diagnosed with a possible allergic reaction to abacavir you MUST STOP taking this medicine immediately, even if other diagnoses are possible. If you stop taking this medicine due to a possible allergic reaction you MUST NEVER take any medicine containing abacavir again, as within hours you may experience a life-threatening lowering of your blood pressure or death. If you have stopped this medicine due to an allergic reaction please return all supplies of the medicine to your pharmacy.
  • It is essential that you read the information on allergic reactions to abacavir that is included in the leaflet supplied with this medicine. There will also be an alert card supplied in your pack of this medicine to remind you and any health professional treating you of the potential for an allergic reaction. You should carry this card with you at all times.
  • It is important that you take this medicine as regularly as possible as directed by your doctor. Try not to miss any doses, as irregular intake of the medicine may increase the chances of experiencing an allergic reaction. If you have stopped taking abacavir for any reason, particularly if due to side effects or other illness, it is important that you contact your doctor before restarting treatment. In some cases your doctor will ask you to restart treatment in a place where you will be able to get ready access to medical care if needed.
  • 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.
  • If you have advanced HIV and a history of opportunistic infections such as pneumocystis carinii pneumonia (PCP) or cytomegalovirus (CMV), you may experience signs and symptoms of inflammation from previous infections soon after you start combination anti-HIV treatment. It is believed that these symptoms are due to an improvement in the body’s immune response, which enables the body to fight infections that may have been present with no obvious symptoms. You should tell your doctor immediately if you experience any signs or symptoms of infection, such as inflammation or high temperature, after starting treatment with this medicine.
  • 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 abacavir, 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.
  • While taking this medicine you should 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

  • People over 65 years of age.
  • Decreased kidney function.
  • Enlarged liver (hepatomegaly).
  • Liver disease.
  • Hepatitis, especially chronic hepatitis B or C.
  • History of alcohol abuse.
  • Obese women.
  • Vitamin B12 deficiency.
  • People with risk factors for heart disease, such as smoking, high blood pressure (hypertension), diabetes or raised cholesterol levels.

Not to be used in

  • Decreased liver function.
  • End stage kidney disease.
  • People with low levels of haemoglobin in their blood.
  • People with low levels of a type of white blood cell called a neutrophil in their blood.
  • This medicine is not recommended for children and adolescents under eighteen years of age.

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 during pregnancy has not been established. It is not recommended for use during pregnancy. Seek medical advice from your doctor.
  • It is recommended that women infected with the HIV virus must not breastfeed their infants under any circumstances, and regardless of their treatment, in order to avoid transmitting the virus to the baby in the breast milk. 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.

Abacavir causes a serious, potentially life-threatening allergic reaction in about 5 out of every 100 people who take the medicine. Further information, including possible symptoms, can be found in the warning section above.

NRTIs such as abacavir, lamivudine and zidovudine can cause a condition called lactic acidosis - see the warning section above.

Combination antiretroviral treatment can cause changes in body fat distribution and raised levels of fats or sugar in the blood - see the warning section above for more information.

Other side effects associated with Trizivir are listed below. Some of these are also possible symptoms of an allergic reaction to abacavir, so it is important to read the warning section above and know when to contact your doctor.

Common (affect between 1 in 10 and 1 in 100 people)

  • Loss of appetite.
  • Headache.
  • Dizziness.
  • Nausea and vomiting.
  • Diarrhoea.
  • Abdominal pain.
  • Rash.
  • Hair loss.
  • Fever.
  • Tiredness (lethargy).
  • Fatigue.
  • Difficulty sleeping (insomnia).
  • Cough.
  • Nasal symptoms.
  • Muscle or joint pain.
  • Decreased levels of white blood cells or red blood cells in the blood (neutropenia or anaemia).

Uncommon (affect between 1 in 100 and 1 in 1000 people)

  • Decreased levels of platelets in the blood (thrombocytopenia).

Rare (affect between 1 in 1000 and 1 in 10,000 people)

  • Inflammation of the pancreas (pancreatitis).
  • Liver disorders such as inflammation of the liver (hepatitis).
  • Anxiety.
  • Depression.
  • Pins and needles sensations.
  • Taste disturbances.

Very rare (affect less than 1 in 10,000 people)

  • Serious skin reactions.

The side effects listed above may not include all of the side effects reported by the medicine'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 make sure that the combination is safe.

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

  • intravenous foscarnet
  • intravenous ganciclovir
  • ribavirin (ribavirin may inhibit effect of zidovudine and the combination carries an increased risk of anaemia)
  • stavudine (zidovudine may inhibit effect of stavudine)
  • 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
  • co-trimoxazole
  • dapsone
  • doxorubicin
  • flucytosine
  • ganciclovir
  • interferon
  • pentamidine
  • pyrimethamine
  • vinblastine
  • vincristine.

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

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 Trizivir and clarithromycin by at least two hours. For more advice ask your pharmacist.

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 this medicine.

There have been reports of a high rate of virological failure and the emergence of resistance at early stage when abacavir and lamivudine were combined with tenofovir as triple therapy.

Tipranavir with ritonavir decreases the level of abacavir and zidovudine in the blood and could therefore make them less effective. This combination is not recommended unless there are no suitable alternatives.

The following medicines may slightly decrease the level of abacavir in the blood and could make it less effective:

  • phenobarbital
  • phenytoin (in addition, zidovudine may alter the blood level of phenytoin)
  • rifampicin.

Abacavir may increase the breakdown of methadone. People dependent on methadone may potentially need their methadone dose adjusting to avoid withdrawal symptoms.

Other medicines containing the same active ingredients

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

Ziagen contains just abacavir.

Epivir contains just lamivudine.

Retrovir contains just zidovudine.

Kivexa contains abacavir and lamivudine.

Combivir contains zidovudine and lamivudine.