Zidovudine

Zidovudine is a synthetic analogue of thymidine (3’-azido-3’- deoxythymidine) also called AZT and nucleoside reverse transcriptase inhibitor (NRTI) used in combination with other agents in the therapy and prophylaxis of the human immunodeficiency virus (HIV) infection and the acquired immunodeficiency syndrome (AIDS). Zidovudine is given to HIV-positive pregnant women to reduce the chance of passing the infection to the baby. Zidovudine works by decreasing the amount of HIV in the blood. Although zidovudine does not cure HIV, it may decrease your chance of developing acquired immunodeficiency syndrome (AIDS) and HIV-related illnesses such as serious infections or cancer. Taking these medications along with practicing safer sex and making other life-style changes may decrease the risk of transmitting (spreading) the HIV virus to other people.

Zidovudine is also used along with other medications in certain situations to treat healthcare workers and other individuals exposed to HIV infection after accidental contact with HIV-contaminated blood, tissues, or other body fluids. Talk to your doctor about the possible risks of using Zidovudine for your condition.

Zidovudine may also be used off-label to treat some conditions associated with human herpesvirus-8 (HHV-8) infection in people with HIV.

Zidovudine was the first antiretroviral agent that was approved for use in treating HIV infection in the United States [1987] ¹ and was subsequently frequently used in antiretroviral regimens for many years. Recently, zidovudine has been replaced by better tolerated nucleoside analogues and it is no longer commonly used in developed countries. Zidovudine is currently indicated for the treatment of HIV infection in combination with other HIV medications such as lamivudine and abacavir.

Zidovudine is available as a single agent in multiple generic forms and under the trade name Retrovir in 100 mg capsules, 300 mg tablets, and as an oral syrup; in combination with lamivudine as Combivir; and in combination with abacavir and lamivudine as Trizivir. The recommended dose of zidovudine in adults is 600 mg orally, daily or 1 mg/kg every 4 hours. Zidovudine is usually taken twice a day by adults and two to three times a day by infants and children. Infants 6 weeks of age and younger may take zidovudine every 6 hours. When zidovudine is taken by pregnant women, it may be taken 5 times a day. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take zidovudine exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor.

Your doctor may temporarily stop your treatment if you experience serious side effects.

Zidovudine controls HIV infection but does not cure it. Continue to take zidovudine even if you feel well. Do not stop taking zidovudine without talking to your doctor. When your supply of zidovudine starts to run low, get more from your doctor or pharmacist. If you miss doses or stop taking zidovudine, your condition may become more difficult to treat.

Zidovudine common side effects include asthenia, constipation, headache, insomnia, loss of appetite, malaise, nausea, and vomiting.

Some side effects of zidovudine can be serious. Serious side effects of zidovudine include lactic acidosis, liver problems, myopathy, and blood disorders such as severe anemia or neutropenia.

Other possible side effects of zidovudine include:

• Changes in your immune system (called immune reconstitution inflammatory syndrome or IRIS). IRIS is a condition that sometimes occurs when the immune system begins to recover after treatment with an HIV medicine. As the immune system gets stronger, it may have an increased response to a previously hidden infection.
• Loss of body fat (lipoatrophy).

Tell your health care provider if you have any side effect that bothers you or that does not go away.

These are not all the possible side effects of zidovudine. To learn more about possible side effects of zidovudine, read the drug label or package insert or talk to your health care provider or pharmacist.

Zidovudine toxicity

Zidovudine can cause serious, life-threatening side effects. These include hypersensitivity reaction or rash, a buildup of lactic acid in the blood (lactic acidosis), liver problems, muscle weakness (myopathy), and blood disorders, such as extremely reduced numbers of red blood cells (severe anemia) or reduced numbers of white blood cells (neutropenia).

Contact your health care provider right away if you have any of the following symptoms that could be signs of a hypersensitivity reaction:

• Rash
• Blistering or peeling of the skin
• Hives
• Itching
• Difficulty breathing or swallowing
• Swelling of the eyes, face, tongue, lips, or throat

Contact your health care provider immediately or get emergency medical treatment right away if you have any of the following symptoms that could be signs of liver problems or lactic acidosis:

• Nausea or vomiting
• Pain in the upper right part of your stomach
• Loss of appetite
• Extreme tiredness
• Weakness
• Dizziness or lightheadedness
• Fast or irregular heartbeat
• Trouble breathing
• Dark-colored urine
• Light-colored bowel movements
• Yellowing of your skin or the whites of your eyes (jaundice)
• Feeling cold, especially in your arms or legs
• Unusual muscle pain

Contact your health care provider if you have any of the following symptoms of myopathy:

• Tiredness
• Muscle pain
• Weakness

Contact your health care provider right away if you have any of the following symptoms of severe anemia or neutropenia:

• Unusual bleeding or bruising
• Fever, chills, or other symptoms of infection
• Unusual tiredness or weakness
• Pale skin

Worsening of liver disease (sometimes resulting in death) has occurred in people with both HIV and hepatitis C virus infection (HCV) who were taking HIV medicines and also being treated for hepatitis C virus infection (HCV) with interferon with or without ribavirin. If you are taking zidovudine as well as interferon with or without ribavirin and you experience side effects, tell your health care provider.

While taking zidovudine, it is important to keep all of your appointments with your health care provider.

Zidovudine mechanism of action

Zidovudine belongs to a group of HIV drugs called nucleoside reverse transcriptase inhibitors (NRTIs). Nucleoside reverse transcriptase inhibitors (NRTIs) block an HIV enzyme called reverse transcriptase. By blocking reverse transcriptase, NRTIs prevent HIV from multiplying and can reduce the amount of HIV in the body.

Zidovudine uses

Zidovudine is a prescription medicine approved by the U.S. Food and Drug Administration (FDA) for the following uses:

• To treat HIV infection in adults and children 4 weeks of age and older. When zidovudine is used to treat HIV infection, the medicine is always used in combination with other HIV medicines.
• To prevent mother-to-child transmission of HIV. When used to prevent mother-to-child transmission, zidovudine is given to women with HIV during pregnancy and childbirth and to their infants for 6 weeks after birth.

Zidovudine is also used along with other medications in certain situations to treat healthcare workers and other individuals exposed to HIV infection after accidental contact with HIV-contaminated blood, tissues, or other body fluids. Talk to your doctor about the possible risks of using Zidovudine for your condition.

Zidovudine may also be used off-label to treat some conditions associated with human herpesvirus-8 (HHV-8) infection in people with HIV.

Zidovudine special precautions

Before taking zidovudine:

• tell your doctor and pharmacist if you are allergic to zidovudine, any other medications, or any of the other ingredients in zidovudine products. Ask your pharmacist for a list of the ingredients.
• tell your doctor and pharmacist what other prescription and nonprescription medications, vitamins, nutritional supplements, you are taking or plan to take. Be sure to mention any of the following: chemotherapy medications for cancer, doxorubicin (Doxil), ganciclovir (Cytovene, Valcyte), interferon alfa, ribavirin (Copegus, Rebetol, Ribasphere), and stavudine (Zerit). Your doctor may need to change the doses of your medications or monitor you carefully for side effects.
• tell your doctor if you have or have ever had kidney disease.
• tell your doctor if you are pregnant, plan to become pregnant, or are breastfeeding. If you become pregnant while taking zidovudine, call your doctor. You should not breastfeed if you are infected with HIV or if you are taking zidovudine.
• you should know that you may have a loss of body fat from your face, legs, and arms. Talk to your doctor if you notice this change.
• you should know that while you are taking medications to treat HIV infection, your immune system may get stronger and begin to fight other infections that were already in your body. This may cause you to develop symptoms of those infections. If you have new or worsening symptoms after starting treatment with zidovudine, be sure to tell your doctor.

It is very important that your doctor check your or your child’s progress at regular visits to make sure that this medicine is working properly. Blood tests may be needed to check for unwanted effects.

Zidovudine may cause blood problems. These problems may result in a greater chance of certain infections and slow healing. Therefore, you should be careful when using regular toothbrushes, dental floss, and toothpicks not to damage your or your child’s gums. Check with your or your child’s medical doctor or dentist if you have any questions about proper oral hygiene (mouth care) during treatment with this medicine.

Check with your doctor if you or your child has muscle pain, tenderness, wasting, or unusual tiredness or weakness while you are using this medicine.

Zidovudine may cause blood and bone marrow problems. Symptoms of bone marrow problems include fever, chills, sore throat pale skin, or unusual tiredness or weakness. These problems may require blood transfusions or temporarily stopping treatment with zidovudine. Check with your or your child’s doctor if any new health problems or symptoms occur while you or your child are taking zidovudine.

Two rare but serious reactions to this medicine are lactic acidosis (too much acid in the blood) and liver toxicity, which includes an enlarged liver. These are more common if you are female, very overweight (obese), or have been taking anti-HIV medicines for a long time. Call your doctor right away if you or your child have more than one of these symptoms: abdominal discomfort or cramping, dark urine, decreased appetite, diarrhea, general feeling of discomfort, light-colored stools, muscle cramping or pain, nausea, unusual tiredness or weakness, trouble breathing, vomiting, or yellow eyes or skin.

Your immune system may get stronger when you start taking HIV medicines. Tell your doctor right away if you or your child notices any changes in your health. Sometimes the immune system will start to fight infections that were hidden in your body, such as pneumonia or tuberculosis. Autoimmune disorders (eg, Graves’ disease, polymyositis, or Guillain-Barré syndrome) may also occur.

This medicine may decrease or lose body fat, especially in your face, arms, legs, or buttocks, when this medicine is used for a long time. Talk to your doctor if you have concerns.

Do not take other medicines unless they have been discussed with your doctor. This includes prescription or nonprescription (over-the-counter [OTC]) medicines and herbal or vitamin supplements.

Zidovudine dose

The dose of Zidovudine will be different for different patients. Follow your doctor’s orders or the directions on the label. The following information includes only the average doses of Zidovudine. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of Zidovudine that you take depends on the strength of the Zidovudine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

For HIV infection:

• For oral dosage forms (capsules, solution, syrup, and tablets):
  • Adults—300 milligrams (mg) 2 times a day in combination with other anti-HIV medicines.
  • Children and infants 4 weeks of age and older—Dose is based on body weight or body size and must be determined by your child’s doctor.
    • Weighs 30 kilograms (kg) or more—600 milligrams (mg) per day or 480 milligrams per square meter of body surface area (mg/m²) a day in divided doses.
    • Weighs 9 kg to less than 30 kg—18 mg per kg per day in divided doses.
    • Weighs 4 kg to less than 9 kg—24 mg per kg per day in divided doses.

To help prevent pregnant women from passing HIV to their babies during pregnancy and at birth:

• For oral dosage form (capsules, syrup):
  • Pregnant women (after 14 weeks of pregnancy, up to the start of labor)—100 milligrams (mg) 5 times a day until the start of labor.
  • Newborn infants—Dose is based on body weight and must be determined by your doctor. The usual dose is 2 milligrams (mg) per kilogram (kg) of body weight every 6 hours starting 12 hours after birth and continuing through 6 weeks of age.
• For oral dosage form (solution):
  • Pregnant women (after 14 weeks of pregnancy, up to the start of labor)—100 milligrams (mg) 5 times a day, 200 mg every 8 hours, or 300 mg every 12 hours until the start of labor.
  • Newborn infants—Dose is based on body weight and must be determined by your doctor. The usual dose is 2 milligrams (mg) per kilogram (kg) (0.9 mg per pound) of body weight every 6 hours starting within 8 to 12 hours of birth and continuing through 6 weeks of age.

What should I do if I forget a dose?

Skip the missed dose and continue your regular dosing schedule. Do not take a double dose to make up for a missed one.

Zidovudine side effects

Zidovudine may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:

• stomach pain or cramps
• heartburn
• diarrhea (especially in children)
• constipation
• headache
• difficulty falling asleep or staying asleep

If you experience the following symptom, or any of those listed in the IMPORTANT WARNING section, call your doctor immediately:

• rash
• blistering or peeling of the skin
• hives
• itching
• difficulty breathing or swallowing
• swelling of the eyes, face, tongue, lips, or throat

More common side effects:

• black, tarry stools
• chills
• cough
• feeling of fullness
• fever
• lower back or side pain
• painful or difficult urination
• pale skin
• right upper abdominal pain and fullness
• sore throat
• stomach pain
• swelling or inflammation of the mouth
• swollen lymph nodes
• ulcers, sores, or white spots in the mouth
• unusual bleeding or bruising
• unusual tiredness or weakness

Rare side effects:

• confusion
• diarrhea
• fast, shallow breathing
• general feeling of discomfort
• loss of appetite
• mood or mental changes
• muscle pain, tenderness, weakness, or cramping
• nausea
• seizures
• sleepiness
• stomach discomfort

Incidence not known:

• back or leg pain
• bleeding gums
• blistering, peeling, or loosening of the skin
• bloating
• blood in the urine
• blurred vision or other change in vision
• bone pain
• burning, crawling, itching, numbness, prickling, “pins and needles”, or tingling feelings
• clay-colored stools
• constipation
• dark urine
• decreased appetite
• decreased urine output
• difficult or labored breathing
• difficulty in moving
• difficulty in swallowing
• dilated neck veins
• dizziness
• extreme tiredness or weakness
• fainting
• fast, irregular, or pounding heartbeat
• general body swelling
• general tiredness and weakness
• headache
• high fever
• hives, skin rash
• hoarseness
• increased need to urinate
• indigestion
• irregular breathing
• irritation or soreness of the mouth
• joint or muscle pain
• lack of coordination
• large, hive-like swelling on the face, eyelids, lips, tongue, throat, hands, legs, feet, or genitals
• light-colored stools
• muscle pain, cramp, spasm, or stiffness
• nosebleeds
• pains in the stomach, side, or abdomen, possibly radiating to the back
• passing urine more often
• puffiness or swelling of the eyelids or around the eyes, face, lips, or tongue
• red skin lesions, often with a purple center
• red, irritated eyes
• redness, soreness, or itching skin
• runny nose
• shakiness in the legs, arms, hands, or feet
• shivering
• sores, welts, or blisters
• stabbing pain
• sweating
• swollen joints
• swollen or painful glands
• tightness in the chest
• trouble sleeping
• unexplained bleeding or bruising
• unpleasant breath odor
• vomiting
• vomiting of blood
• weight gain
• yellow eyes or skin

Some side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

More common

• difficulty having a bowel movement
• headache (severe)
• lack or loss of strength
• muscle soreness
• weight loss

Less common

• bluish-brown colored bands on nails
• changes in skin color

Incidence not known

• belching
• heartburn
• stomach cramps

Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.

1. Kemnic TR, Gulick PG. HIV Antiretroviral Therapy. [Updated 2019 Feb 15]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2019 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK513308[↩]