Final answer:
The Durham-Humphrey Amendment to the Federal Food, Drug, and Cosmetic Act created RX Only (prescription drugs) and OTC (over-the-counter drugs).
Step-by-step explanation:
The amendment to the Federal Food, Drug, and Cosmetic Act that created RX Only (prescription drugs) and OTC (over-the-counter drugs) is The Durham-Humphrey Amendment.
The Durham-Humphrey Amendment was passed in 1951 and it established a clear distinction between prescription and non-prescription drugs. It allowed medical professionals to prescribe medications that could only be obtained with a prescription, while certain medications were determined to be safe for use without a prescription and could be sold directly to consumers over-the-counter.
This amendment has had a significant impact on the regulation and accessibility of medications in the United States.