When the agency that runs Medicare announced last week that it would take action against doctors who prescribe abusively in its massive drug program – perhaps banning them – it raised an interesting question. What exactly constitutes "abusive" prescribing? On this point, the Centers for Medicare and Medicare and Medicaid Services (CMS) is treading carefully, refusing to get pinned down by numerical thresholds for specific drugs. Instead Medicare will consider a variety of factors in deciding whether a physician's drug choices pose a "threat to the health or safety" of seniors and the disabled.