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FDA Regulation of Animal Drugs

A Brief Overview of FDA's Legal Marketing Statuses for Animal Drugs
Classifying Prescription, Veterinary Feed Directive and Over-The-Counter Drugs
Dispensing Veterinary Prescription Drugs
Requirements for Labeling On Manufactured Prescription Animal Drugs
Unapproved Animal Drugs
   Compounding of Animal Drugs
Extra-Label Use of FDA Approved Drugs In Animals
Information about Extra-Label Use of Specific Drug Products
How to Report Animal Drug and Device Side Effects and Product Problems
Animal Drug Shortage Information

A Brief Overview of FDA's Legal Marketing Statuses for Animal Drugs

Under the Federal Food, Drug, and Cosmetic Act (the “Act”), the term "drug" means articles recognized in the official United States Pharmacopoeia, official Homeopathic Pharmacopoeia of the United States, or official National Formulary; articles intended for use in the diagnosis, cure, mitigation, treatment, or prevention of disease in man or other animals; and articles other than food intended to affect the structure or any function of the body of man or other animals. It also includes articles intended for use as a component of a drug.

Once a product is determined to be a drug for animal use, the next step is to determine whether or not it is a new animal drug. The Act defines a new animal drug (in part) as any drug intended for use for animals other than man, the composition of which is not generally recognized, among experts qualified by scientific training and experience, as safe and effective for use under the conditions prescribed, recommended, or suggested in its labeling. By virtue of Supreme Court interpretations of the necessary basis for general recognition, there are, for all practical purposes, no animal drugs which are not also new animal drugs.

Under the Act, a new animal drug may not be legally introduced into interstate commerce unless it is the subject of either: 

  • an approved new animal drug application (NADA) or abbreviated new animal drug application (ANADA) under section 512 of the Act; 
  • a conditional approval (CNADA) under section 571 of the Act;
  • a listing on the Legally Marketed Unapproved New Animal Drug Index for Minor Species (the Index) under section 572 of the Act;
  • an emergency use authorization (EUA) under section 564 of the Act; or
  • an investigational exemption under section 512(j) of the Act. 

Pathways to Legal Marketing Status


An approved animal drug has gone through the New Animal Drug Application (NADA) process, or for an approved generic animal drug, the Abbreviated New Animal Drug Application (ANADA) process. If the information in the application meets the requirements for approval, FDA approves the animal drug. FDA’s approval means the drug is safe and effective when it is used according to the label. FDA’s approval also ensures that the drug’s strength, quality, and purity are consistent from batch to batch, and that the drug’s labeling is truthful, complete, and not misleading.

Learn more about the NADA and ANADA approval processes as well as the requirements for an investigational exemption by visiting the following webpage:

Conditional Approval

Conditional approval (CNADA) is only available for some animal drugs for use in a minor species or in a major species under special circumstances. A conditionally approved animal drug has gone through FDA's drug approval process except the drug has not yet met the effectiveness standard for full approval. FDA’s conditional approval means that when used according to the label, the drug is safe and has a “reasonable expectation of effectiveness.” FDA's conditional approval also means that the drug is properly manufactured.

The conditional approval is valid for one year. The drug company can ask FDA to renew the conditional approval annually for up to four more years, for a total of five years of conditional approval. During the 5-year period, the drug company can legally sell the animal drug while collecting the remaining effectiveness data. After collecting the remaining effectiveness data, the company submits an application to FDA for full approval. The agency reviews the application and, if appropriate, fully approves the drug.

Learn more about the conditional drug approval process by visiting the following webpage:


An indexed animal drug is a drug on FDA’s Index of Legally Marketed Unapproved New Animal Drugs for Minor Species, referred to simply as “the Index.” As the name says, a drug listed on the Index is unapproved but has legal marketing status. It can be legally sold for a specific use in certain minor species. Indexing is allowed for drugs for:

  • Non-food-producing minor species, such as pet birds, hamsters, and ornamental fish. These animals are typically not eaten by people or by other animals that produce food for people to eat; and
  • An early non-food life stage of a food-producing minor species, such as oyster spat (immature oysters). Because people do not generally eat oyster spat, a drug to treat a disease in spat can be indexed, but a drug to treat a disease in adult oysters, which people commonly eat, cannot be indexed.

Indexing a drug is quite different from the drug approval process. Indexing relies heavily on a panel of qualified experts outside FDA. The experts review the drug’s safety in the specific minor species and the drug’s effectiveness for the intended use. All experts on the panel must agree that, when used according to the label, the drug’s benefits outweigh the risks to the treated animal. If FDA agrees with the panel, the agency adds the drug to the Index.

Learn more about indexing by visiting the following webpage:

Emergency Use Authorization

The Emergency Use Authorization (EUA) authority allows FDA to help strengthen the nation’s public health protections against chemical, biological, radiological, and nuclear (CBRN) threats including infectious diseases, by facilitating the availability and use of medical countermeasures needed during public health emergencies.

When the Secretary of HHS declares that an emergency use authorization is appropriate, FDA may authorize unapproved medical products or unapproved uses of approved medical products to be used in an emergency to diagnose, treat, or prevent serious or life-threatening diseases or conditions caused by CBRN threat agents when certain criteria are met, including that there are no adequate, approved, and available alternatives. The HHS declaration to support such use must be based on one of four types of determinations of threats or potential threats by the Secretary of HHS, Homeland Security, or Defense.

Learn more about the EUA process by visiting the following webpage:

More Information

Approved Animal Drug Products (Green Book)
Animal Drugs @ FDA Explained

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Classifying Prescription, Veterinary Feed Directive, and Over-The-Counter Animal Drugs

During the drug approval or indexing process, FDA is responsible for determining the marketing status of animal drug as prescription, over-the-counter, or veterinary feed directive. 

One difference between these three marketing statuses of animal drugs is whether or not veterinary oversight is required for the safe and effective use of the drug. If adequate “directions for use” can be written on the drug’s label in such a way that a non-veterinarian can use the drug safely and effectively, then the drug company can market the animal drug as over-the-counter (OTC). If not, then the drug company must market the animal drug as either prescription or veterinary feed directive (VFD).

Both prescription and VFD drugs require veterinary oversight to be used safely and effectively. The main difference between these two statuses of animal drugs is whether the drug is used in or on animal feed. When the drug is for use in or on animal feed (a medicated feed), FDA can approve it as a VFD drug. When the drug is not for use in or on animal feed, it must be a prescription drug. While use of VFD drugs requires veterinary oversight, VFD drugs are not prescription drugs. Congress introduced VFD to ensure the veterinarians’ involvement in the process of determining when to use a VFD drug, but without subjecting such involvement to state pharmacy laws, as prescription status would. In short, assigning prescription drug status to a medicated feed would be practically unworkable. 

A prescription animal drug can be dispensed only by or on the lawful written order of a licensed veterinarian and must have the following statement on the label:

"Caution: Federal law restricts this drug to use by or on the order of a licensed veterinarian."

A VFD is a written order issued by a licensed veterinarian in the course of the veterinarian’s professional practice that authorizes the client (the owner or other animal caretaker) to obtain and use a VFD medicated feed. A product containing a VFD animal drug must have the following statement on the label:

‘‘Caution: Federal law restricts medicated feed containing this veterinary feed directive (VFD) drug to use by or on the order of a licensed veterinarian.’’

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Dispensing Prescription Animal Drugs

Because adequate directions for safe and effective lay use cannot be written for prescription animal drugs, such products can only be sold on the prescription or other order of a licensed veterinarian. Prior to being sold or dispensed, they must remain in the possession of a person or firm regularly and lawfully engaged in the manufacture, transportation, storage, or wholesale or retail distribution of animal prescription drug products. The drugs may be distributed only by persons or firms authorized by State law.

Sale (dispensing, shipping, or otherwise making available for use in animals) of a prescription animal drug to a layperson may be made only by or on the bona fide prescription or other order of a licensed veterinarian. Sale of a prescription animal drug to a layperson, except on a prescription or on order of a licensed practitioner, causes the drug to be misbranded and subjects the seller to civil and/or criminal provisions of the Act.

A licensed veterinarian may legally use or dispense a prescription animal drug only within the course of her/his professional practice (e.g., where a valid veterinarian-client-patient relationship exists). Veterinarians employed by drug manufacturers or distributors may not legally dispense prescription drugs to laypersons unless they meet the above criteria. Similarly, practicing veterinarians or their employees may not legally sell prescription animal drugs to walk-in customers unless the same criteria are met.

The following information must be included on the label of prescription animal drugs dispensed by filling the lawful order of a licensed veterinarian:

  • name and address of the dispenser;
  • serial number and date of the order or its filling;
  • name and address of the veterinarian who prescribed or ordered the drug product;
  • directions for use; and
  • any necessary warning and precautionary statements (e.g., withdrawal times).

Veterinarians must include the appropriate applicable information (above) in their prescription to allow it to be dispensed.  Veterinarians must also follow State laws for dispensing animal drugs.

Veterinarians should make efforts to ensure their instructions are followed, especially when they prescribe or recommend drugs for food-producing animals that require a withdrawal period.

Requirements for Labeling On Manufactured Prescription Animal Drugs

In addition to the labeling requirements generally applicable to animal drugs, federal regulations require at least the following information on the label of the finished package form of prescription animal drugs:

  • the statement, “Approved by FDA under NADA # XXX-XXX”  if the drug is an approved and marketed brand name animal drug; or the statement, “Approved by FDA under ANADA # XXX-XXX” if the drug is an approved and marketed generic animal drug; 
  • the statement, "Caution: Federal law restricts this drug to use by or on the order of a licensed veterinarian;"
  • recommended or usual dosage;
  • route of administration, if it is not for oral use;
  • quantity or proportion of each active ingredient as well as the information required by section 502(e) of the Act;
  • names of inactive ingredients if it is for other than oral use;
  • an identifying lot or control number from which it is possible to determine the complete manufacturing history of the drug.

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Unapproved Animal Drugs

Unapproved new animal drugs are animal drugs that don’t have legal marketing status. They have not been approved, conditionally approved, indexed, or authorized by FDA. It’s illegal to market unapproved new animal drugs because they haven’t gone through the FDA pre-market review and obtained legal marketing status under the FD&C Act. Unapproved animal drugs may not meet the agency’s strict standards for safety and effectiveness and may not be properly manufactured or properly labeled and packaged. Unapproved animal drugs include animal drugs compounded from bulk drug substances.

More information:

Unapproved Animal Drugs

Compounding of Animal Drugs

As described above, under the Federal Food, Drug, and Cosmetic Act (FD&C Act), to be legally marketed new animal drugs must be approved, conditionally approved, included on the Index of Legally Marketed Unapproved New Animal Drugs for Minor Species, or authorized for emergency use. The FD&C Act does not generally distinguish between compounding and other methods of animal drug manufacturing.  New animal drugs that are not approved, conditionally approved, indexed, or authorized, which includes drugs compounded from bulk drug substances, are considered "unsafe" and “adulterated” under the FD&C Act.

FDA recognizes that in some situations a drug compounded from bulk drug substances may be the only appropriate treatment option for a particular animal. On April 22, 2022, FDA finalized Guidance for Industry #256, “Compounding Animal Drugs from Bulk Drug Substances,” which addresses situations in which the FDA generally does not intend to take action for certain violations of the Food, Drug, & Cosmetic Act when pharmacists and veterinarians compound or oversee the compounding of animal drugs from bulk drug substances:

  • to fill patient-specific prescriptions for nonfood-producing animals
  • to compound “office stock” (certain drugs kept in veterinarians’ supply) for nonfood-producing animals and
  • to compound antidotes for food-producing animals or sedatives and anesthetics for free-ranging wildlife.

Animal drugs compounded from bulk drug substances do not undergo review by FDA, meaning that the FDA has not determined these unapproved animal drugs to be safe and effective for their intended uses. Because of the safety benefits and protections of the pre-market review process and post-market monitoring of FDA-approved, conditionally approved, indexed and authorized drugs, veterinarians should only consider using drugs compounded from bulk drug substances when FDA-approved, conditionally approved, indexed, or authorized drugs are not available to treat the animal.

More information:

Animal Drug Compounding

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