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Factrel (Canada)

This page contains information on Factrel for veterinary use.
The information provided typically includes the following:
  • Factrel Indications
  • Warnings and cautions for Factrel
  • Direction and dosage information for Factrel


This treatment applies to the following species:
Company: Zoetis

DIN 00573760





FACTREL (gonadorelin for injection USP) is a sterile solution of synthetic luteinizing hormone/ releasing hormone (LRH) intended for intramuscular administration.

Active Ingredients

Each mL of sterile solution contains gonadorelin (as hydrochloride salt), 50 µg.

Preservatives: Benzyl alcohol 2% w/v.

Factrel Indications

As an aid in the treatment of cystic ovaries in cattle. For use in repeat breeder dairy cows on or at the time of their third or greater service.

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

Factrel Dosage And Administration

Cystic Ovaries: 2 mL (100 µg) as a single intramuscular injection.

Repeat Breeders: 2 mL (100 µg) to be administered intramuscularly as a single injection on or at the time of cow’s third or greater service.

For use with LUTALYSE (dinoprost tromethamine) Sterile Solution to synchronize estrous cycles to allow fixed-time artificial insemination (FTAI) in lactating dairy cows: Administer 2 mL FACTREL Injection (100 mcg gonadorelin) per cow as an intramuscular injection in a treatment regimen with the following framework:

● Administer the first dose of FACTREL Injection (2 mL) at Day 0

● Administer LUTALYSE (25 mg dinoprost, as dinoprost tromethamine) Sterile Solution by intramuscular injection 6-8 days after the first dose of FACTREL Injection.

● Administer a second dose of FACTREL Injection (2 mL) 30 to 72 hours after the LUTALYSE injection.

● Perform FTAI 0 to 24 hours after the second dose of FACTREL Injection, or inseminate cows on detected estrus using standard herd practices.

Below are three examples of treatment regimens for FTAI that fit within the dosage regimen framework described immediately above:


Example 1

Example 2

Example 3

Day 0 (Monday)




Day 7 (the following Monday)




Day 9 (Wednesday)

2nd FACTREL + FTAI at 48 hours after LUTALYSE

2nd FACTREL 48 hours after LUTALYSE

2nd FACTREL 56 hours after LUTALYSE

Day 10 (Thursday)


FTAI 24 hours after 2nd FACTREL

FTAI 18 hours after 2nd FACTREL


Treated animals must not be slaughtered for use in food for at least 7 days after the latest treatment with this drug.

No milk withholding time is required when used according to the label.

Keep out of reach of children.

Clinical Pharmacology

FACTREL’s (gonadorelin hydrochloride) chemical name is 5 - oxo - L - propyl - L - histidyl - L - tryptophyl - L - seryl - L - tyrosyl - glycyl - L - leucyl - L - arginyl - L - prolyl - glycinamide hydrochloride.

Its molecular formula is C55H75H17O13 X HCl (X = 1 ~ 2), and it has a molecular weight of 1219 to 1255 depending on its hydrochloric acid content. It is structurally identical to the natural Luteinizing Hormone/Releasing Hormone (LRH) isolated from porcine or ovine hypothalami. The hydrochloride salt of gonadorelin used in FACTREL is a water-soluble white powder. It is synthesized by the classical solution method, and is virtually free of extraneous peptides or amino acids.


Gonadorelin (GnRH) induces ovulation when administered subcutaneously on the day of proestrus. It acts by augmentation of anterior pituitary secretion of the gonadotropins, Luteinizing Hormone (LH) and Follicle Stimulating Hormone (FSH). Gonadorelin’s capacity to cause secretion of LH was found to be equal to that of LH/FSH-RH of natural origin.

In the treatment of cystic ovaries, FACTREL was demonstrated to be safe and effective at a clinical dose of 100 µg. Clinically it has been demonstrated that breeder cows treated with GnRH, at their third or greater services, showed a 51.1% conception rate, as opposed to a 43.2% conception rate for the control group.


Gonadorelin did not elicit any signs of toxicity and was not lethal after intravenous administration of single doses of 100 mg/kg in mice and of single doses of 150 mg/kg in rats. Following 28 consecutive days IV administration in mature rats at doses of 5, 25 and 50 µg/kg/day secondary pharmacology or hormonal changes were observed in treated males. These changes included decreased seminal vesicle weight (all doses), decreased body weight and prostatic weight (25 µg/kg or greater). These organ and body weight changes are regarded as secondary effects resulting from gonadotrophin release and the feed-back mechanism to high circulating levels of LH. There were no drug-related histopathologic alterations of seminal vesicle or prostate. In treated females, body and organ weights were comparable to the controls and there were no drug-related histopathologic alterations. In monkeys receiving daily doses of 500 µg of gonadorelin for 28 days and in monkeys receiving either 4, 20 or 100 µg/kg/day from day 8 to day 15 of each animal’s cycle, survival body weight, food consumption, clinical laboratory parameters, organ weights, gross and microscopic observations were not affected. No biologically significant changes in clinical chemistry parameters were observed.


Teratology studies were carried out in pregnant female mice, rats (two strains) and rabbits. Daily doses of gonadorelin up to 100 µg/kg were administered subcutaneously on days 6 through 15 of pregnancy in mice and rats, and on days 6 through 18 of gestation in rabbits. The administration of the compound, at doses of 100 µg/kg or less, did not produce any toxic effects in the dams or fetuses of the species tested.


Do not freeze. Store between 2 and 7°C. Contents should be used within 30 days after the first dose is removed.


FACTREL is available in 20 and 50 mL vial sizes.

Zoetis is a trademark and Factrel and Lutalyse are registered trademarks of Zoetis or its licensors, used under license by Zoetis Canada Inc.

Zoetis Canada Inc., Kirkland QC H9H 4M7



CPN: 1198370.4

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