With just a handful of prescriptions to his name, psychiatrist Ernest Bagner III was barely a blip in Medicare’s vast drug program in 2009. But the next year he began churning them out at a furious rate. Not just the psych drugs expected in his specialty, but expensive pills for asthma and high cholesterol, heartburn and blood clots. By the end of 2010, Medicare had paid $3.8 million for Bagner’s drugs 2014 one of the highest tallies in the country. His prescriptions cost the program another $2.6 million the following year, records analyzed by ProPublica show. Bagner, 46, says there’s...