In 1962, Congress amended the Federal Food, Drug and Cosmetic Act to provide greater regulation of drugs sold in the United States. Under those amendments, all new drugs must be shown by adequate studies to be both “safe and effective” before they can be marketed. Drugs approved as merely “safe” prior to 1962 (i.e. those approved between 1938 and 1962) had to be reviewed as to their effectiveness under the Drug Efficacy Study Implementation (”DESI”) program. A DESI review of over 3,400 drugs that entered the market between 1938 and 1962 was undertaken in the 1960s and 1970s. If the DESI review indicated a lack of substantial evidence of a drug’s effectiveness for all of its labeled indications, the FDA published a Notice of Opportunity for a hearing concerning its proposal to withdraw approval of the drug for marketing. A manufacturer of that drug, or drugs “identical, related or similar” (”IRS”) to that drug, could request a hearing and attempt to provide evidence of the drug’s effectiveness. Drugs for which a Notice of Opportunity for hearing has been published are referred to as “less-than-effective” (”LTE” or “DESI-LTE”) drugs until they receive FDA approval. The IRS counterpart of a DESI-LTE drug is also considered less than effective. “DESI drugs” and “Less Than Effective” drugs are not Covered Outpatient Drugs under the Medicaid program.
There are still hundreds of DESI drugs on the market. The sale of unapproved drugs is illegal. See FDA’s Final (2006) Marketed Unapproved Drugs – Compliance Policy Guide.