An obscure injectable medication made from pigs' pituitary glands has surged up the list of drugs that cost Medicare the most money, taking a growing bite out of the program's resources. Medicare's tab for the medication, H.P. Acthar Gel, jumped twentyfold from 2008 to 2012, reaching $141.5 million, according to Medicare prescribing data requested by ProPublica. The bill for 2013 is likely to be even higher, exceeding $220 million. Acthar's explosive growth illustrates how Medicare's prescription drug program — perhaps more than private health insurers and even other public health programs — is struggling to contain the taxpayer burden of expensive therapies aimed at rare conditions.