The Animal Drug Availability Act (H.R. 2508) (“ADAA”), signed by the President on October 9, 1996, amended the Federal Food, Drug, and Cosmetic Act to provide new flexibility to the way FDA regulates new animal drugs and medicated feeds.

The law was intended to increase the number of approved new animal drugs on the market and was supported by FDA's Center for Veterinary Medicine and a coalition of animal industry groups which included manufacturers of animal health products, veterinarians, and livestock producers. ADAA made changes that were intended to benefit the animal health industry and the nation's animals without compromising FDA's mission to protect the public health. The changes introduced by ADAA include:

• amended the definition of substantial evidence of effectiveness, making the process FDA uses to evaluate and approve new animal drugs more flexible. This change eliminated the requirement for field studies and expanded the types of studies that FDA could consider in support of a finding of substantial evidence of effectiveness.
• provided for more interaction between animal drug sponsors and the FDA during the drug development process. The law requires FDA to grant a presubmission conference, if requested by the sponsor, to discuss the drug development at its earliest stages. The purpose of a presubmission conference is for FDA and the sponsor to agree on the data needed to establish safety and effectiveness, and the types of studies that can be conducted to generate such data.
• provided a procedure for establishing import tolerances for residues of new animal drugs not approved or conditionally approved for use in the United States but lawfully used in other countries and present in imported, animal-derived food and food products. Import tolerances provide a basis for importing and legally marketing such animal-derived food and food products in the United States.
• created a new category of drugs, "Veterinary Feed Directive Drugs," that allows the approval and use of new animal drugs in animal feed, on a veterinarian's order.
• permitted a range of acceptable/recommended doses to appear on new animal drug product labeling, rather than one optimum dose.
• In addition, the law gives direction to FDA on how to review supplements that seek to add a minor use or minor species indication to an approved application.

Since enactment in 1996, ADAA’s provisions have been implemented by FDA in the following regulations:

• 21 CFR § 514.4 – Substantial evidence.
• 21 CFR § 514.5 – Presubmission conferences.
• 21 CFR § 514.117 – Adequate and well-controlled studies.
• 21 CFR § 558.6 – Veterinary feed directive drugs.

In addition, a proposed rule regarding import tolerances was published in the Federal Register on January 25, 2012.