In December 1995, a new class of drugs called protease inhibitors was added to the earlier approved class of nucleoside analogs, which included Retrovir (zidovudine, also known as AZT), Videx (didanosine, or ddI), Hivid (zalcitabine, or ddC), Zerit (stavudine, or d4t), and Epivir (lamivudine, or 3TC).

In September 1997, FDA approved Combivir, an AZT-and-3TC combination medicine for AIDS and HIV infection. Because AZT and 3TC are frequently prescribed with one another, the combination of the 2 drugs in one tablet or capsule is convenient.

Zidovudine, ZDV, azidothymidine or AZT has been an anticancer drug since 1964 and used as an antiretroviral drug since 1985. An example of AZT dosage is 500 mg/day as 2 250 mg tablets every 12 hours has zidovudine and lamivudin. Twice a day capsules of Combivir have 150 mg of lamivudin and 300 mg of AZT.