Also called Iamivudine or Epivir. Often prescribed with AZT as part of HIV combined therapy. It will stop HIV from infecting cells which are clear of the virus, but will not have any effect on cells already infected. It's used both to control existing infection and to prevent new infection... if you're going to be taking 3TC/AZT as prophylactic treatment after exposure to possibly HIV-infected material, it's a good idea to start within a couple of hours.