Medicare Part D, passed in 2003, has significantly reduced seniors’ spending on prescription drugs. But the coverage hasn’t protected Leslie Ross from near calamity. The 72-year-old diabetic needs insulin to stay alive. The prices of these drugs have skyrocketed, forcing her to supplement her long-lasting insulin, Lantus, with more frequent use of a less-expensive insulin. This one remains in her body only four hours, requiring more vigilance to control her blood sugar. To cut her Lantus bills – nearly $1,700 this year – she has sometimes resorted to buying unused supplies from other diabetics on eBay. “You take your chances when you do stuff like that,” she said. “I checked that the vial hasn’t been opened. It still had t…