Spending on prescription drugs in Medicare Part D increased 17% from 2013 to 2014, according to data released by CMS. Drug costs in the program grew from $104 billion to $121 billion between 2013 and 2014, the data shows. The data set is compiled from drugs paid for by Medicare Part D, including 38 million beneficiaries. That's about 70% of all Medicare beneficiaries. The data comes from claims from more than 1 million providers. Lisinopril, a drug used to treat high blood pressure and heart failure, was the most commonly used drug, according to the 38,278,860 total claims submitted. In total, $281,614,340 was spent on the drug, according to the data. But according to total drug cost, Sovaldi, a drug used to treat hepatitis C, was the most expensive, with $3,106,589,192 spent on the drug. Comparatively, just 109,543 claims were submitted for Sovaldi.