Anti-HIV Drug: Zidovudine (AZT)

Brand name: Retrovir
Other names: Zidovudine, ZDV; azido-deocythymidine
Type of drug: Antiretroviral, Anti HIV

Used for. AZT is used for the management of HIV infection in adults with CD4+ counts less than 500. It is routinely prescribed for people infected with HIV showing clinical symptoms of the disease or having CD4+ counts less than 200. It is commonly used, at the discretion of the physician and the infected individual, for people with CD4+ counts between 200 and 500. It has been tested, but not proven effective, in people with CD4+ counts greater than 500. It is sometimes given to people immediately after HIV exposure through needle stick or other hospital exposure although it isn’t known whether the drug is effective in preventing the virus, once it is inside their bodies, from infecting these people.

AZT is also used to reduce the risk of mother-to-child transmission of the virus during pregnancy and birth and to treat HIV-infected children over three months of age who have HIV-related symptoms or who are asymptomatic, with significant HIV-related suppression of their immune systems.

General Information. AZT is the most widely used and best-known antiretroviral agent. It mimics a naturally occurring building block of DNA and works by interfering with reverse transcription, a process essential for the replication of HIV.

In more than seven years of clinical testing, the value of AZT has been confirmed repeatedly for people infected with HIV who have clinical symptoms of the disease. Because it was the first anti-HIV drug, AZT has become the standard against which new treatments are usually compared, whether or not it is the ”best” drug. However, AZT is not a cure for HIV infection or AIDS< and people who use it may continue to experience HIV-related symptoms, opportunistic infections, and declining immune=system function. Controversies exist, however, about when to begin AZT and when to continue with it, add another therapy, or change to other therapies.  AZT is available as capsules, syrup, and as sterile solution for intravenous injection.

Treatment. The recommended dose of AZT for adults is 500 to 600 mg per day. For 500 mg per day, a 100 mg capsule may be taken five times a day (approximately every three to four hours), or the total amount may be split into three unequal doses (200 mg, 100 mg, 200 mg) taken every eight hours.

Because AZT is known to cross the blood-brain barrier, high doses of the drug have sometimes been used to treat AIDS-related dementia. The dose used to treat dementia is 1,000 mg per day. Because the causes of dementia may vary, diagnosing and treating the cause (whenever possible) is important. Possible causes include HIV, CMV, toxoplasmosis, and B-vitamin deficiencies. If AZT causes serious side effects, reducing the dose or discontinuing the drug may be necessary.

Cautions and Warnings. AZT should not be used by anyone with a known allergy to it. AZT is metabolized by the liver and eliminated from the body primarily through the kidneys. Consequently, the drug should be used with caution by people with kidney or liver disease.

Side Effects. Side effects occur more frequently in people taking high doses of AT (greater than 600 mg per day) or in people with more advanced disease at the time therapy is started. The most common side effects of AZT are headaches, nausea, hypertension, and a general sense of feeling ill. These side effects may be due to the drug itself or to the person’s anxiety about taking it. Often these common side effects disappear after a few weeks of therapy.

The most serious side effects of AZT are anemia, granulocytopenia, and myopathy. Anemia is a deficiency in the red blood cells cause by suppression of the bone marrow. AZT-caused anemia can be treated y reducing the doses, switching to another antiretroviral drug, providing a transfusion, or by using a drug called erythropoietin (EPO), which stimulates production of red blood cells. Transfusions are recommended only for severe anemia. EPO cannot replace a transfusion if the anemia is severe.

Granulocytopenia is a lowering of the white blood cell counts, particularly cells called neutrophils, which are active in fighting bacterial infection. Like anemia, it is caused by suppression of the bone marrow. AZT-caused granulocytopenia can be treated with a colony stimulating factor (G-CSF), which stimulates the production of white blood cells. G-CSF is preferred over the other commonly available colony-stimulating factor (GM-CSF) because it is better tolerated and is less likely to cause an increase in HIV replication.

Myopathy is a weakness or degeneration of the muscle tissue. It can be caused by HIV infection itself or by long-term treatment with AZT.