Medicare is wasting hundreds of millions of dollars a year by failing to rein in doctors who routinely give patients pricey name-brand drugs when cheaper generic alternatives are available. ProPublica analyzed the prescribing habits of 1.6 million practitioners nationwide and found that a tiny fraction of them are having an outsized impact on spending in Medicare's massive drug program. Just 913 internists, family medicine and general practice physicians cost taxpayers an extra $300 million in 2011 alone by disproportionately choosing name-brand drugs. These doctors each wrote at least 5,000 prescriptions that year, including refills, and ranked among the program's most prolific prescribers.