LOS ANGELES, Calif.—A University of Southern California (USC) study released July 6 comparing Medicare prescription drug prices with those paid by Costco members found that the federal government overpaid on roughly half of the most common generic medicines in 2018. The study—which appears as a research letter in JAMA Internal Medicine—compared Medicare Part D prescription drug prices with those paid by Costco members, and found that across more than 1.4 billion Medicare Part D claims for 184 products, Medicare plans overspent by 13 percent in 2017 and almost 21 percent in 2018 compared to Costco member prices. It also found Medicare plans paid more than Costco members on almost 53 percent of 90-day fills analyzed in 2018. On all 30- and 90-day prescription fills, Medicare plans overpaid 43 percent of the time. “Efforts to reduce prescription drug prices tend to focus on brand-name medicines, but the opaque pharmaceutical supply system …