Which agency is primarily responsible for the regulation of controlled substances?

The Drug Enforcement Administration (DEA) is the federal agency primarily tasked with the regulation of controlled substances in the United States. This responsibility encompasses the enforcement of the Controlled Substances Act (CSA), which classifies drugs into schedules based on their potential for abuse, medical usage, and safety profile.

The DEA is involved in the oversight of the manufacturing, distribution, and dispensing of these substances. It ensures that pharmaceutical companies, healthcare providers, and pharmacies comply with federal regulations related to controlled substances, and it has the authority to conduct investigations and enforce laws against violations of these regulations, including improper prescribing and unlawful distribution of controlled drugs.

In contrast, other agencies listed have different roles: the Food and Drug Administration (FDA) focuses on drug approval and safety, the National Institutes of Health (NIH) is dedicated to medical research, and the Environmental Protection Agency (EPA) regulates environmental issues. Thus, the specific function of the DEA in regulating controlled substances makes it the correct answer in this context.