Epivir (lamivudine) belongs to class of anti-HIV drugs known as nucleoside reverse transcriptase inhibitors (NRTIs). NRTIs act as fake versions of the building blocks HIV needs, preventing HIV from making copies of itself. Epivir is always combined with other anti-HIV drugs. It is an ingredient in Combivir (zidovudine/lamivudine), Trizivir (zidovudine/lamivudine/abacavir), and Epzicom (abacavir/lamivudine). Epivir is not usually effective for people who have already taken Emtriva (emtricitabine) and developed resistance to it.