Shop Rx Act of 2019 This bill provides statutory authority for certain provisions of the Centers for Medicare & Medicaid Services rule titled "Modernizing Part D and Medicare Advantage to Lower Drug Prices and Reduce Out-of-Pocket Expenses," published on May 23, 2019. The rule requires, in part, Medicare prescription drug plan sponsors to implement an electronic, real-time benefit tool that is capable of integrating with at least one prescriber's electronic prescribing system or electronic health record. The tool must provide prescribers with patient-specific, real-time formulary and benefit information, including information regarding cost-sharing, formulary alternatives, and utilization management requirements. The rule takes effect January 1, 2021.