Animal & Veterinary

FACTREL - Veterinarians

July 2, 2013
Revised April 24, 2015

Dear Bovine Veterinarian:

In June 2013, FDA approved the second gonadotropin releasing hormone (GnRH) product, FACTREL, for estrous synchrony in lactating dairy cows. FACTREL is a sterile injectable solution of gonadorelin hydrochloride, and when used with LUTALYSE (dinoprost tromethamine) as part of a synchronization regimen, the drug can be used to synchronize estrous cycles to allow fixed time artificial insemination in lactating dairy cows. FDA also wants to remind you of the benefits of using FDA- approved drugs.

Drug Information

 Factrel Injection
ManufacturerZoetis Inc.
Application TypeNew Animal Drug Application (NADA)
Application Number139-237
New Indication

For use with LUTALYSE (dinoprost tromethamine) Sterile Solution to synchronize estrous cycles to allow fixed-time artificial insemination (FTAI) in lactating dairy cows.

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

Active IngredientGonadorelin hydrochloride
Concentration50 mcg gonadorelin (as gonadorelin hydrochloride)/mL
How Supplied20 mL multi-dose vials
Dispensing StatusPrescription
Route of AdministrationIntramuscular injection
Dosage Regimen

The recommended intramuscular dosage is 100 to 200 mcg of gonadorelin (2 to 4 mL) per cow, used in estrous synchrony programs similar to the following:

  • Administer the first dose of FACTREL (2 to 4 mL) at Day 0.
  • Administer LUTALYSE (25 mg dinoprost, as dinoprost tromethamine) by intramuscular injection 6 to 8 days after the first dose of FACTREL.
  • Administer a second dose of FACTREL (2 to 4 mL) 30 to 72 hours after the LUTALYSE injection.
  • Perform FTAI 0 to 24 hours after the second dose of FACTREL, or inseminate cows on detected estrous 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.

FACTREL is a sterile solution of synthetic gonadorelin and has the identical amino acid sequence as endogenous gonadorelin.

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

Please refer to the Freedom of Information Summary and package insert for FACTREL 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 InjectionGONABREED Injectable SolutionFERTAGYL
ManufacturerZoetis Inc.Parnell Technologies Pty LtdIntervet Inc.
Active IngredientGonadorelin hydrochlorideGonadorelin acetateGonadorelin acetate
For Estrous Synchrony, Use With:LUTALYSE (dinoprost tromethamine)Cloprostenol sodiumESTRUMATE (cloprostenol injection)
Species/ClassLactating 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 FACTREL, 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, FACTREL and LUTALYSE synchronize estrous cycles to allow 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

Page Last Updated: 04/24/2015
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