this is a more complicated situation. First, for biologics, there are rarely equivalent generics (context: https://www.jhsph.edu/news/news-releases/2016/generic-biolog...). Second, this is a case where Genentech (the maker of Avastin and Lucentis) is basically trying to prevent people from prescribing a cheaper drug that can be substituted. Genentech's made the argument that Lucentis is specifically designed for this use, while Avastin has issues (safety and efficacy). Doctors have some latitude to prescribe off-label drugs where there is an indication it's safe and effective. In this case, doctors are basically subdividing avastin packets (which has a risk).