Dear Bovine Veterinarian:

FDA wants to tell you about the recent approval of the third gonadotropin releasing hormone (GnRH) product, FERTAGYL, for estrous synchrony in lactating dairy cows. FERTAGYL is a sterile injectable solution of gonadorelin acetate, and when used with ESTRUMATE (cloprostenol injection) as part of a synchronization regimen, the drug can be used to synchronize estrous cycles to allow for fixed time artificial insemination in lactating dairy cows. FDA also wants to remind you of the benefits of using FDA- approved drugs.

Drug Information




Intervet Inc

Application Type

Abbreviated New Animal Drug Application (ANADA)

Application Number


New Indication

For use with ESTRUMATE (cloprostenol injection) to synchronize estrous cycles to allow for fixed time artificial insemination (FTAI) in lactating dairy cows.

(FERTAGYL is already approved for the treatment of cystic ovaries in dairy cattle.)

Active Ingredient

Gonadorelin acetate


43 mcg gonadorelin (as gonadorelin acetate)/mL

How Supplied

20 mL multi-dose vial

Dispensing Status


Route of Administration

Intramuscular injection

(FERTAGYL may be given by either intramuscular or intravenous injection for the treatment of cystic ovaries.)

Dosage Regimen

The recommended intramuscular dosage is 86 mcg of gonadorelin (2 mL) per cow, used in estrus synchrony programs similar to the following:

·         Administer the first FERTAGYL injection (2 mL) on Day 0.

·         Administer 2 mL of ESTRUMATE (500 mcg cloprostenol, as cloprostenol sodium) by intramuscular injection 6 to 8 days after the first FERTAGYL injection.

·         Administer the second FERTAGYL injection (2 mL) 30 to 72 hours after the ESTRUMATE injection.

·         Perform FTAI 8 to 24 hours after the second FERTAGYL injection, or inseminate cows on detected estrus using standard herd practices.

Clinical Pharmacology

Endogenous gonadorelin is the gonadotropin releasing hormone (GnRH) that causes the anterior pituitary gland to release gonadotropins, such as luteinizing hormone (LH) and follicle-stimulating hormone (FSH). Endogenous gonadorelin is synthesized and/or released from the hypothalamus during various stages of the bovine estrous cycle following appropriate neurogenic stimuli.

FERTAGYL is a sterile solution of synthetic gonadorelin and is physiologically and chemically identical to endogenous gonadorelin.

Endogenous gonadorelin, through release of LH, induces ovulation of dominant ovarian follicles present on the bovine ovary during the estrous cycle. FERTAGYL has the same effect as endogenous gonadorelin to induce ovulation.

Please refer to the Freedom of Information Summary and package insert for FERTAGYL before using the drug.

Benefits of FDA Approval

FDA rigorously evaluates an animal drug before approving it. As part of the approval process, the drug company must prove to FDA that:

·         The drug is safe and effective for a specific use in a specific animal species;

·         The manufacturing process is adequate to preserve the drug’s identity, strength, quality, and purity; and

·         The drug’s labeling is truthful and non-misleading.

For a drug intended to be used in food-producing animals, FDA’s approval process also ensures that food products, such as milk and meat, from treated animals are safe for people to eat.

FDA’s role does not stop after the agency approves an animal drug. As long as the drug company markets the animal drug, the agency continues to monitor:

·         The drug’s safety and effectiveness. Sometimes, the agency’s post-approval monitoring uncovers safety and effectiveness issues that were unknown at the time of approval;

·         The manufacturing process to ensure quality and consistency are maintained; and

·         The drug’s labeling to make sure the information remains truthful and non-misleading.

Other Gonadorelin Products

Five gonadorelin (GnRH) products are FDA-approved to treat cystic ovaries in dairy cows, but only three are also FDA-approved for use with another drug for synchronizing estrous cycles in lactating dairy cows: GONABREED, FACTREL, and FERTAGYL.

FDA-approved GnRH Products for Use with Another Drug for Estrous Synchrony


FACTREL Injection

GONABREED Injectable Solution



Zoetis Inc.

Parnell Technologies Pty Ltd

Intervet Inc.

Active Ingredient

Gonadorelin hydrochloride

Gonadorelin acetate

Gonadorelin acetate

For Estrous Synchrony, Use With:

LUTALYSE (dinoprost tromethamine)

Cloprostenol sodium

ESTRUMATE (cloprostenol injection)


Lactating dairy cows

Lactating dairy cows and beef cows

Lactating dairy cows

Other than the three uses listed in the table above, it is illegal to use GnRH products with another drug for estrous synchrony.

By prescribing FDA-approved FERTAGYL, you’re choosing one of the three marketed GnRH products shown to be safe and effective for use with another drug for synchronizing estrous cycles in lactating dairy cows. Used together in a breeding program, FERTAGYL and ESTRUMATE synchronize estrous cycles to allow for fixed time artificial insemination in lactating dairy cows.

FDA’s Center for Veterinary Medicine (CVM) is committed to promoting and protecting animal health by ensuring safe and effective drugs are available for animals. For more information, please contact CVM’s Education & Outreach Staff at 240-402-7002 or


Daniel G. McChesney, Ph.D.
Director, Office of Surveillance and Compliance
FDA Center for Veterinary Medicine