Which federal regulatory agency is focused on safeguarding the health of the public by ensuring the safety and efficacy of medications?

The Food and Drug Administration (FDA) is the federal regulatory agency that is primarily responsible for protecting public health by overseeing the safety, efficacy, and security of medications, as well as other biological products and medical devices. The FDA's role includes reviewing new drug applications, monitoring adverse drug reactions, and ensuring that pharmaceuticals meet specific approval standards before they can be marketed. This regulatory oversight is crucial in maintaining the integrity of the drug approval process and ensuring that patients receive safe and effective medications.

In contrast, the other agencies listed have different areas of focus. The Environmental Protection Agency (EPA) is dedicated to protecting human health and the environment by enforcing regulations related to environmental safety but does not oversee medication safety. The Centers for Medicare and Medicaid Services (CMS) primarily focuses on health care financing and delivering specific health services rather than drug safety. Lastly, the Health Resources and Services Administration (HRSA) mainly works to improve access to healthcare services for people who are uninsured or living in rural areas, without a direct role in the regulation of drug safety.

Thus, the FDA is the agency that directly addresses the safety and efficacy of medications, making it the correct answer.