Zidovudine and Lamivudine act by terminating the growth of the DNA chain and inhibiting the reverse transcriptase of HIV, where as Nevirapine is a non-nucleoside reverse transcriptase inhibtor.
This combination is used in the management of the HIV infection. since all 3 of these drugs are to be administered twice daily, a fixed dose combination is created, with each tablet containing half the commonly prescribed doses of Lamivudine, Zidovudine and Nevirapine.