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  1. Product Safety Information

Steroid Hormone Implants Used for Growth in Food-Producing Animals


Since the 1950s, the Food and Drug Administration (FDA) has approved a number of steroid hormone drugs for use in beef cattle and sheep, including natural estrogen, progesterone, testosterone, and their synthetic versions. These drugs increase the animals’ growth rate and the efficiency by which they convert the feed they eat into meat.

All approved steroid implant products have a zero day withdrawal. This means that the meat from the animal is safe for humans to eat at any time after the animal is treated. No steroid hormone implants are approved for growth purposes in dairy cows, veal calves, pigs, or poultry. The majority of the steroid hormone implants are available for over-the-counter purchase in the U.S. and are generally given by the livestock producer at specific stages of the animals’ growth.

The FDA approves these drugs only after information and/or studies have shown that the food from the treated animals is safe for people to eat, and that the drugs do not harm the treated animal or the environment. The drugs also have to be effective, meaning that they work as intended. The labeling for each product provides all instructions for safe and effective use and is approved by FDA. The labeling of the indication(s) for use of each implant reflects the physiological status and management of animals used in the regulatory studies conducted to support the new animal drug approval. For each approved product, the FDA also makes available to the public via its website a Freedom of Information Summary that summarizes the information that FDA used to determine that the drug is safe for the treated animals, the animal products (edible tissues such as meat) are safe for humans to eat, and that the product is effective.

FDA asked sponsors of steroid implants to update their labeling by July 1, 2023, to clarify if the product is approved for repeated implantation (reimplantation) within a single production phase. Consequently, if the labeling of a steroid implant does not specify it is approved for reimplantation, only one ear implant may be given to an animal during a single production phase. A list of the currently approved and marketed implants and their conditions of use is available here.

These steroid hormone drugs are typically formulated as pellets or “implants” that are placed under the skin on the back side of the animal’s ear. The implants dissolve slowly under the skin and do not require removal. The ears of the treated animals are discarded at slaughter and are not used for human food. Using scientific data, FDA establishes the acceptable safe limits for hormones in meat. A safe level for human consumption is a level of drug in the meat that would be expected to have no harmful effect in humans based on extensive scientific study and review.

Naturally-Occurring Hormones

Some of the approved drugs are naturally produced throughout life in people and animals, such as estradiol (estrogen), progesterone, and testosterone. These natural hormones are necessary for normal development, growth, and reproduction. People are not at risk from eating food from animals treated with these drugs because the amount of additional hormone following drug treatment is very small compared with the amount of natural hormones that are normally found in the meat of untreated animals and that are naturally produced in the human body.

Synthetic Hormones

Some of the approved drugs are synthetic versions of the natural hormones, such as trenbolone acetate and zeranol. Just like the natural hormone implants, before FDA approved these drugs, FDA required information and/or toxicological testing in laboratory animals to determine safe levels in the animal products that we eat (edible tissues). Furthermore, FDA required that the manufacturers demonstrate that the amount of hormone left in each edible tissue after treatment is below the appropriate safe level. As described above, a safe level is a level which would be expected to have no harmful effect in humans.

Extralabel Use

Extralabel use of cattle ear implants by veterinarians or non-veterinarians for growth-promoting purposes is illegal.

When an approved human or animal drug is used in a way other than what is stated on the drug’s labeling, it is an extralabel use. This is sometimes referred by the public as an “off-label” use because the drug is used in a way that’s “off the label.” Under specified conditions of use, only veterinarians are legally allowed to prescribe approved human and animal drugs for extralabel use in animals. Non-veterinarians are not permitted to use drugs in an extralabel manner without the oversight of a veterinarian. This applies to FDA-approved prescription and over-the-counter drugs.

Veterinarians must follow all federal requirements addressing the extralabel use of drugs in animals, as detailed in FDA regulations (Title 21, Code of Federal Regulations, Part 530). Use of a growth-promoting cattle ear implant in an extralabel manner, including those with an Rx marketing status, does not comply with these requirements, which limits extralabel use only to treatment situations when the health of an animal is threatened, it is suffering, or death may result from failure to treat. Extralabel use of a drug for growth-promotion purposes does not qualify for this permitted limited use. Illegal extralabel use can result in a drug being considered adulterated and subject to possible enforcement action.

Additional Information

Information about approved hormonal implant products can be found in the Code of Federal Regulations (CFR), Title 21, Parts 522 and 556. Paper copies of the CFR may be found at your local public or university library and are for sale from the Superintendent of Documents, U.S. Government Printing Office, Washington, DC 20402. In addition, the Electronic Code of Federal Regulations may be found on the Internet: https://www.ecfr.gov/.

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