In vitro a u některých pacientů infikovaných HIV- 1 byla pozorována rezistence na emtricitabin nebo tenofovir, z důvodu substituce M184V nebo M184I v RT pro emtricitabin nebo substituce K65R v RT tenofovir.
Resistance to emtricitabine or tenofovir has been seen in vitro and in some HIV-1 infected patients due to the development of an M184V or M184I substitution in RT with emtricitabine or a K65R substitution in RT with tenofovir.