In 1968, the U.S. Food and Drug Administration (FDA) formed the Drug Efficacy Study Implementation (DESI) to implement recommendations of the National Academy of Sciences investigation of effectiveness of drugs first marketed between 1938 and 1962.

Congress amended the Federal Food, Drug, and Cosmetic Act in 1962 to require that new drugs be shown effective, as well as safe, to obtain FDA approval. The amendment required FDA to evaluate the effectiveness of the drugs the agency had approved only for safety between 1938, when Congress enacted the FD&C Act requiring new drugs be shown safe prior to marketing, and 1962.

FDA contracted with the National Academy of Sciences/National Research Council (NAS/NRC) to make an initial evaluation of the effectiveness of more than 3,400 drugs that had been approved only for safety between 1938 and 1962. The agency reviewed and reevaluated the NAS/NRC reports and published its initial findings in Federal Register notices.

DESI covered the drugs reviewed by NAS/NRC, as well as the even larger number of drugs that entered the market—without FDA approval—as identical, related or similar to those covered by safety-only FDA approvals.

FDA’s final DESI determination classifies a drug as either effective for one or more of its labeled indications or lacking substantial evidence of effectiveness for one or more of its labeled indications. Most DESI proceedings have been closed and FDA’s findings have been published in the Federal Register.