Zidovudine was the first drug approved to treat HIV infection in the United States.
Often called AZT, zidovudine is a nucleoside reverse-transcriptase inhibitor. It blocks reverse transcriptase, an HIV enzyme the virus needs to copy its genetic material and reproduce inside human cells.
The U.S. Food and Drug Administration approved zidovudine in 1987, only a few years after HIV had been identified as the cause of AIDS. The approval followed clinical evidence that the drug could extend survival in people with advanced HIV, although its early use was limited by toxicity and the development of drug resistance.
Zidovudine was initially used alone, but modern HIV treatment relies on combinations of medicines from different drug classes. A common mix-up is treating AZT as a vaccine: it is an antiviral medicine, not a preventive vaccine. Zidovudine also became important in reducing mother-to-child HIV transmission.