Only two health care providers prescribed $10 million or more worth of drugs under Medicare Part D in 2011, but that number rose to 70 last year, and the number topping the $5 million mark rose from 41 to 514 over the same period. Prescriptions of Gilead Sciences’ hepatitis C treatments Harvoni and Sovaldi, as well as expensive drugs for cancer, multiple sclerosis and rheumatoid arthritis, drove much of the increase.