A nurse in an emergency department is planning care for a client who is having an acute myocardial infarction (MI). The nurse should plan to administer which of the following medications after the initial acute phase to manage the client's pain and anxiety?

Rationale: A. Oxygen is administered during the initial acute phase if the client is hypoxic, to improve myocardial oxygenation, but it does not directly manage pain or anxiety once stabilized. B. Nitroglycerin is used to relieve chest pain and reduce myocardial workload, primarily in the acute phase of MI. Its use after stabilization is for ongoing ischemia, not specifically for anxiety or persistent pain. C. Aspirin is an antiplatelet therapy that prevents further clot formation and is continued long-term for MI management, but it does not address acute pain or anxiety. D. Morphine is indicated after the initial acute phase to manage persistent chest pain and anxiety. It works by reducing myocardial oxygen demand through vasodilation and providing analgesia and sedation, making it appropriate for pain and anxiety management post-acute MI.