What main requirement does the Food, Drug, and Cosmetic Act of 1938 impose on new drugs?

The Food, Drug, and Cosmetic Act of 1938 primarily requires that new drugs be proven safe for use before they can be marketed. This landmark legislation was enacted in response to safety concerns regarding pharmaceuticals, particularly following incidents where harmful substances were being marketed without adequate testing. The Act emphasizes the necessity for manufacturers to provide scientific evidence of a drug's safety while not yet mandating proof of its effectiveness. This foundational requirement established a regulatory framework aimed at ensuring public health and safety, significantly shaping how drugs are developed, tested, and introduced into the market.

The other options do not reflect the main requirement outlined in the Act. While proving effectiveness is imperative in later stages and under subsequent regulations, safety was the primary concern of this initial legislation. Advertising to consumers and child-resistant packaging, although important in their respective contexts, do not address the core stipulations of the 1938 Act regarding the introduction of new drugs.