For many years CMS has paid for "drug wastage," for example, if a physician opens a one-time-use 20 mg vial, gives a patient 17 mg, then the other 3 mg can be billed as wastage (Parman, 2016 here). For a 2016 review by Bach and colleagues in BMJ, here.
In a new article in Health Affairs, July 9, 2021, Peter Bach revisits this while reviewing a recent report by the National Academy of Medicine on drug wastage (here).
His main reference point is a 173-page report released by National Academies in February 2021 which got less attention at that time (Capitol riots, COVID third wave, inauguration) - here, here.
CMS had posted its own review of drug wastage 2017-2019 a few weeks earlier, in December 2020 here.