What is Retrovir used for?
- Treating HIV infection. Zidovudine must be used in combination with other anti-HIV medicines (cART).
- Preventing HIV infection being passed from pregnant women to their developing babies (by treating pregnant women and their newborn babies). In some situations it may be appropriate for zidovudine to be used on its own for this purpose, for example if the mother doesn't yet need cART for herself because she has a very low viral load and high CD4 count. However, combination therapy is usually preferred, because this maximises the chance of preventing transmission and also represents optimal therapy for the mother. Zidovudine is also given to the baby once it is born, to treat any HIV infection that might have been passed to it from the mother during delivery.
How does Retrovir work?
Retrovir capsules, oral solution and infusion all contain the active ingredient zidovudine (also known as azidothymidine or AZT), which is a type of medicine called a nucleoside reverse transcriptase inhibitor. Zidovudine is also available without a brand name, ie as the generic medicine. It is 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 works 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 is one of several medicines that lower the amount of virus in the body (viral load), help the immune system to recover, and therefore slow down or stop the progression of the disease from HIV to AIDS.
A combination of several anti-HIV medicines is required to fight HIV because the virus can become resistant to one agent very quickly. This is known as combined antiretroviral therapy (cART) or highly active antiretroviral therapy (HAART). Zidovudine is used in combination with other anti-HIV drugs that attack the HIV virus in different ways. This minimises the virus's ability to replicate and multiply, and helps prevent it becoming resistant to treatment.
How do I take Retrovir?
- Zidovudine is usually taken twice a day, morning and evening, as part of cART. Follow the instructions given by your doctor. These will also be printed on the dispensing label that your pharmacist has put on the packet of medicine.
- Taking zidovudine to prevent transmission of HIV to the baby during pregnancy is a specialist area and it is important to follow the instructions given by your specialist.
- Zidovudine can be taken either with or without food.
- The capsules should be swallowed whole with a drink of water. The oral solution may be more appropriate for people who have difficulty swallowing the capsules whole.
- You must keep taking this medicine regularly every day unless your doctor tells you to stop.
Important information about Retrovir
- 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 of the medicines 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 make sure that you take all your doses at the correct time, and that you visit your doctor for repeat prescriptions before you run out of medicine.
- Treatment of HIV infection with anti-HIV medicines such as this one has been shown to reduce the risk of transmitting the virus to other people through sexual contact. However, it does not remove this risk entirely. 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.
- 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.
- The class of medicines that zidovudine belongs 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 its 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, red blood cells or platelets in the blood. You should consult your doctor immediately if you experience any of the following symptoms, as they may indicate a problem with your blood cells: unexplained bruising or bleeding, purple spots, sore throat, mouth ulcers, high temperature (fever) or other signs of infection, feeling tired or general illness.
- If you have any problems with your liver, in particular chronic hepatitis B or C, you should have regular blood tests to monitor your liver function while you are taking this medicine.
Retrovir should be used with caution in
- People over 65 years of age.
- People with decreased kidney or liver function.
- People with liver disease, particularly hepatitis B or C.
- People with an enlarged liver (hepatomegaly).
- People with a history of alcohol abuse.
- Obese women.
- People with vitamin B12 deficiency.
Retrovir should not be used in
- People with low levels of haemoglobin in their blood.
- People with low levels of white blood cells called neutrophils in their blood (neutropenia).
- New-born babies with high levels of bilirubin in their blood (hyperbilirubinaemia - making the skin appear yellow or jaundiced) requiring treatment other than phototherapy (light therapy).
- New-born babies with blood levels of liver transaminase enzymes that are over five times greater than normal.
- Retrovir oral solution is not suitable for people with rare hereditary problems of fructose intolerance.
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.
- Zidovudine can be taken by HIV-positive pregnant women to reduce the risk of transmitting HIV to their unborn child. The benefit of reducing the risk of HIV infection in the baby outweighs any risk that may be associated with the medicine. You can get further medical information and advice about the risks of the medicine from your doctor.
- Combined antiretroviral therapy is widely used to help prevent transmission of HIV infection from a pregnant woman to her developing baby. This should only be prescribed by specialists in HIV infection and it is important to get medical advice from your doctor straight away if you think you could be pregnant while you are taking this medicine.
- In the UK it is currently recommended that women infected with HIV should not breastfeed their infants, regardless of their treatment, in order to avoid transmitting the virus to the baby in the breast milk. Mothers are advised to feed their babies with formula from birth. You should discuss this with your doctor.
Possible side effects of Retrovir
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, it does not mean that all people using this medicine will experience that or any side effect.
Very common (affect more than 1 in 10 people)
- Feeling sick.
Common (affect between 1 in 10 and 1 in 100 people)
- Abdominal pain.
- Pain in the muscles.
- General feeling of being unwell (malaise).
- Decrease in the number of red blood cells (anaemia) or white blood cells (neutropenia) in the blood - see the warning section above.
- Raised liver enzymes.
Uncommon (affect between 1 in 100 and 1 in 1000 people)
- Shortness of breath.
- Decrease in the number of platelets in the blood (thrombocytopenia).
- Excess gas in the stomach or intestines (wind or flatulence).
- Rash or itching.
- Feeling weak.
Rare (affect between 1 in 1000 and 1 in 10,000 people)
- Taste disturbance.
- Loss of appetite.
- Anxiety and depression.
- Pins and needles sensations (paraesthesia).
- Difficulty concentrating.
- Difficulty sleeping (insomnia).
- Flu-like symptoms.
- Raised levels of lactic acid in the blood (lactic acidosis) - see the warning section above.
- Heart muscle problems.
- Chest pain.
- Inflammation of the pancreas (pancreatitis).
- Changes in the colour of your nails, skin, or the skin inside your mouth.
- Nettle-type rash (hives).
- Increased need to pass urine.
- Enlargement of the breasts in men.
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.
If you think you have experienced a side effect from a medicine or vaccine you should check the patient information leaflet. This lists the known side effects and what to do if you get them. You can also get advice from your doctor, nurse or pharmacist. If they think it's necessary they'll report it for you.
You can also report side effects yourself using the yellow card website: www.mhra.gov.uk/yellowcard.
How can Retrovir 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 zidovudine is not used in combination with the following medicines:
- ribavirin (the combination has an increased risk of anaemia)
- rifampicin (may make zidovudine less effective)
- stavudine (zidovudine may inhibit the effect of stavudine).
Zidovudine may affect the blood level of the antiepileptic medicine phenytoin. This may need to be monitored if you take both these medicines.
The antibiotic clarithromycin may reduce the absorption of zidovudine from the gut and could make it less effective. To avoid this, these medicines should be taken at least two hours apart.
Tipranavir may reduce the blood level of zidovudine and could make it less effective.
The following medicines may increase the blood level of zidovudine and may therefore increase the risk of its side effects:
- valproic acid.
There may be an increased risk of side effects on the blood cells or kidneys if zidovudine is used in combination with other medicines that can decrease blood cells or have side effects on the kidneys, such as the following:
- IV pentamidine
If your doctor decides you need treatment with any of these medicines while you are taking zidovudine, you may need extra monitoring of your kidney function and levels of blood cells.
The weight loss medicine orlistat has been reported to reduce the absorption of anti-HIV medicines from the gut and could make them less effective.
Other medicines containing the same active ingredient
Zidovudine capsules are also available without a brand name, ie as the generic medicine.
Combivir contains zidovudine in combination with another anti-HIV medicine called lamivudine. These tablets are also available generically.
Trizivir contains zidovudine in combination with two other anti-HIV medicines called abacavir and lamivudine.
For background information about our medicine factsheets, including the references used to produce them, click here.