Which act created the two classes of drugs, prescription (Rx) and over-the-counter (OTC)?

The act that established the two classes of drugs, prescription and over-the-counter, was the Durham-Humphrey Amendment. This amendment, enacted in 1951, specifically addressed the classification of medications and established a clear distinction between drugs that could be dispensed only with a doctor's prescription (Rx) and those that could be purchased over-the-counter (OTC) without the need for a prescription.

This classification is significant in ensuring that certain medications, which may require more direct supervision by a healthcare professional due to potential risks or side effects, are only available through a prescription. On the other hand, OTC medications are deemed safe for use by the general public without the need for a healthcare provider's oversight. The creation of these classes has played a crucial role in public health by regulating drug access based on safety and usage guidelines.

The other options represent earlier legislative efforts that contributed to drug regulation but did not specifically establish the prescription and OTC drug distinction. The 1911 Shirley Amendments were intended to amend the earlier Pure Food and Drug Act of 1906 to address misleading labels but did not create the drug classes. The 1938 Federal Food, Drug, and Cosmetic Act broadened the scope of regulation but did not specifically categorize drugs as Rx or OTC