Zidovudine (AZT): What You Need to Know

Zidovudine, often called AZT, is one of the oldest antiretroviral drugs used to treat HIV. It slows viral replication and lowers the amount of virus in the blood when combined with other HIV medicines. People still use it today as part of combination therapy, for post-exposure prophylaxis (PEP) and to reduce mother-to-child transmission during pregnancy and delivery.

How zidovudine works is simple: it blocks reverse transcriptase, the enzyme HIV uses to copy its genetic material. That prevents the virus from making more copies of itself. Zidovudine is a nucleoside reverse transcriptase inhibitor (NRTI). It works best when taken with other antiretrovirals, because using a single drug lets the virus develop resistance quickly.

Uses and dosing

For adults on combination antiretroviral therapy, a common oral dose is 300 mg twice daily. For PEP after potential exposure, zidovudine often joins two other drugs for a short course, usually 28 days. Pregnant people may be prescribed zidovudine to cut the risk of transmission to the baby; dosing and timing vary and healthcare teams tailor it to each case. Children and infants get doses based on weight; always follow pediatric dosing exactly.

Side effects, monitoring, and practical tips

The most common side effects are nausea, headache, fatigue and muscle aches. Zidovudine can cause bone marrow suppression, leading to anemia and low white blood cell counts. Your provider will usually monitor a full blood count early and during treatment. Rare but serious problems include lactic acidosis and liver toxicity; report unusual tiredness, stomach pain, rapid breathing or yellowing skin right away.

Drug interactions matter. Combining zidovudine with other drugs that depress bone marrow can increase risk of anemia. Some antivirals may not pair well with zidovudine, so always tell your clinician about every medicine you take, including supplements.

Take zidovudine at the same times each day to keep levels steady. If you miss a dose, take it as soon as you remember unless it is almost time for the next dose; don’t double up. You can take tablets with or without food, but food may reduce nausea for some people. Store tablets at room temperature away from moisture and heat.

Zidovudine comes as tablets and oral solution; generics make it affordable in many places. In some delivery settings clinicians use IV zidovudine during labor. Check with your insurer or local pharmacy for coverage and price options.

HIV can become resistant if zidovudine is used alone or if doses are missed. That’s why it’s usually part of combination therapy. Zidovudine has played a key role in preventing mother-to-child transmission, but breastfeeding recommendations depend on local guidance and individual circumstances, so talk with your provider.

Avoid unknown online sellers. Buy from licensed pharmacies and check packaging and expiration dates. If side effects or interactions concern you, call your healthcare team. Zidovudine is effective when used correctly, but it requires monitoring and good adherence to work well.