Under the Freedom of Information Act, ProPublica obtained data on the prescriptions written by more than 1.6 million providers in the Medicare Part D program in 2011.

Our analysis focused on the nearly 364,000 providers who wrote at least 50 prescriptions, including refills, for one drug. For each provider, we calculated a name-brand dispensing rate, and for comparison, we determined the overall rate for every medical specialty in each state.

We identified as outliers providers who were at least two standard deviations from the mean in their specialty and state. These included about 11,750 who had name-brand prescribing rates that were higher than their peers and 3,000 who had name-brand prescribing rates that were lower.

To estimate the cost of high name-brand prescribing, we looked at primary care doctors, who treat many conditions for which generics are readily available. (We excluded doctors who regularly use costly HIV/AIDS drugs for which there are few generics.)

We identified 913 primary care doctors who wrote at least 5,000 prescriptions in 2011 as outliers. They accounted for more than $1 billion in drug spending. If their average cost had equaled that of their peers, Medicare would have saved more than $300 million in 2011 alone.

Next, we matched these 913 prescribers against our Dollars for Docs database of payments for speaking, consulting, research, meals and gifts made by 15 pharmaceutical companies since 2009.

Results showed that 48 percent of the prescribers with high rates of name brand use received at least $1,000 from the companies, excluding research.

To compare, we selected a random sample of 1,000 primary care doctors who were not disproportionate name-brand users. Of those, only 15 percent received at least $1,000 in payments.