Revia and Vivitrol® (naltrexone injection) contain the same active ingredient (naltrexone). However, they are given in different ways -- Revia comes as a tablet that is taken by mouth, while Vivitrol is an injectable form of naltrexone. Vivitrol is given as an intramuscular injection (an injection into the muscle).
Vivitrol is only available as a brand-name product at this time. This is because it is currently protected by patents that prevent manufacturers from making a generic version (see Generic Vivitrol).