Extra-Label Use in Pets: Why FDA Approval Pathway Changes What a Veterinarian May Do

The phrase "off-label" does not apply the same way to every animal drug. Under US federal rules, a veterinarian may prescribe certain extra-label uses of approved drugs. For conditionally approved and indexed animal drugs, FDA states that extra-label use is not allowed, and those products must be used as their labeling says.

So the first question is not whether a veterinarian can use a drug off-label. The first question is which legal pathway the product came through.

Start with the proposed use

Extra-label use means using a drug in a way that does not follow its approved labeling. FDA's regulation (21 CFR 530.3) gives examples: a species not listed on the label, an indication not listed, or a dose, frequency or route different from the label.

Suppose a veterinarian proposes a use that differs from the label. The answer depends on the product's pathway, and each pathway leads to a different branch.

• Approved animal drug. FDA's AMDUCA framework lets a veterinarian consider extra-label use under federal conditions. Those conditions include a valid veterinarian-client-patient relationship (VCPR) and a lawful veterinarian order.

• Approved human drug. The same AMDUCA conditions apply. The drug's human approval is what places it in this branch. It does not mean the drug is established as safe or effective for your pet.

• Conditionally approved animal drug. FDA says extra-label use is not allowed. The product must be used as its labeling states.

• Indexed animal drug. FDA says extra-label use is not allowed. This pathway covers certain minor species, such as pet birds, hamsters and ornamental fish.

• Pathway cannot be identified. If you cannot tell which category the product is in, do not assume extra-label flexibility. Identify the product first.

How the pathways differ

FDA notes that indexed drugs do not appear in Animal Drugs @ FDA or the Green Book. A product missing from those two databases may therefore be indexed. A product missing from all three sources has an unverified legal status.

Conditional approval is easy to misread. FDA describes it as a way to market a drug for a limited time while the effectiveness requirement is completed. It does not lower the approval requirements. FDA says the initial conditional approval lasts one year, with up to four annual renewals if the company shows progress. That is not the same as full approval, and it does not create ordinary extra-label flexibility.

What AMDUCA permits for approved drugs

AMDUCA is the Animal Medicinal Drug Use Clarification Act of 1994. FDA says it permits veterinarians to prescribe extra-label uses of certain approved animal drugs and approved human drugs under defined conditions. The implementing regulations are in 21 CFR Part 530.

Four points matter for a pet owner.

• A veterinarian's lawful order is required. The extra-label use must be by or on the lawful written or oral order of a licensed veterinarian within a valid VCPR. FDA states that without a valid VCPR, using an approved new animal drug for an unlabeled use causes the drug to be deemed unsafe and adulterated under the federal Food, Drug, and Cosmetic Act.

• Self-directed use is not covered. FDA lists extra-label use by a lay person as not permitted, except under a licensed veterinarian's supervision. Using a human prescription on your pet because the active ingredient looks similar is not what AMDUCA describes.

• Health must be at stake. FDA says extra-label use is limited to circumstances where the animal's health is threatened, or suffering or death may result from failure to treat. Extra-label use to enhance production is not permitted.

• The dispensed product needs complete labeling. For a drug prescribed or dispensed for extra-label use, the label or accompanying information must include the prescribing veterinarian's name and address, the active ingredient, and the veterinarian's directions for use. Those directions cover the animal identified, dose, frequency, route and duration. It must also include cautionary statements and any withdrawal or discard times for food-producing animals.

FDA also maintains a list of drugs prohibited from extra-label use (21 CFR 530.41), and it may prohibit extra-label use of a drug in non-food animals if it finds a public health risk. Some drugs are off the table even for a veterinarian.

These rules describe federal requirements. State veterinary practice laws and pharmacy rules can add further conditions, and this article does not address them.

Limits of this framework

This article covers non-food pets. FDA's rules for food-producing animals add further conditions, including withdrawal periods, identification of treated animals and measures to prevent drug residues in meat, milk or eggs. Do not apply the pet pathway to an animal that may enter the food supply.

Compounding is a separate topic. FDA states that AMDUCA does not permit animal drug compounding from bulk active pharmaceutical ingredients. Compounded products are not covered by the approval pathways above.

Nothing here tells you whether a particular drug is appropriate or safe for your pet. A human drug is not approved for pets just because it contains a familiar ingredient. Whether any extra-label use is appropriate is a clinical decision for the veterinarian who examines your animal.

Label and database markers that settle the pathway

The product's own label is the best starting point. FDA states that you cannot tell if a drug is legally marketed by looking at the tablet or smelling the solution.

1. Find the application statement. Look for "Approved by FDA under NADA" or "ANADA," the "Conditionally approved" wording, or the "THIS PRODUCT IS INDEXED—MIF" statement.

2. Read the number exactly. Approved and conditionally approved products carry a six-digit application number. Indexed products carry a six-digit MIF number.

3. Check the database. Search Animal Drugs @ FDA or the Green Book for approved and conditionally approved drugs. Search the Index for indexed minor-species drugs.

4. Do not rely on the same brand name. FDA explains that one approved drug can be marketed under several labels from different distributors, each with its own brand name. The application number is the more reliable identifier.

5. Ignore weak signals. FDA says an NDC number does not show that a drug is legally marketed. The same goes for the veterinarian-prescription caution statement and phrases such as "made in an FDA-registered facility." Under federal law, manufacturers must register and list their drugs, including unapproved ones, and the NDC is assigned to every listed drug.

A person who cannot find a reliable number should treat the pathway as unidentified. Showing the veterinarian or pharmacist the full label is more useful than describing the product from memory.

Questions to bring to the veterinarian

Take the product label or a clear photo of it. Then ask the following.

• Is this the labeled use? Is the proposed use for my pet's species, condition, dose, frequency and route the one stated on the label? If not, which part differs?

• Which pathway is it? Is this product approved, conditionally approved or indexed? What application or MIF number is printed on it?

• Is extra-label use allowed here? If the use is not on the label, is this a product for which extra-label use may be considered under AMDUCA? If it is conditionally approved or indexed, does that mean it must be used exactly as labeled?

• Is the product the exact one you prescribed? Does the brand, ingredient, strength and form on my bottle match what you intended? Was it dispensed by a pharmacy against your order?

• Is a human drug involved? Why is this human drug being considered, and what monitoring and safety limits apply to my pet?

• Is the pet's status clear? Is my animal considered a non-food pet? Could any food-animal rules apply, such as for a backyard animal?

• What if the label and instructions disagree? If the pharmacy label, product label and your directions differ, whom should I contact before giving another dose?

If a product label shows the conditionally approved or indexed statement and the proposed use goes beyond it, ask the veterinarian to identify the labeled alternative or explain why the labeled use applies. If you cannot identify the product at all, that is the first thing to resolve.

References

• FDA: Animal Medicinal Drug Use Clarification Act of 1994 (AMDUCA)

• FDA: Lions and Tigers and Bears! OMUMS!

• FDA: How can I tell if a drug is legally marketed for animals?