Veterinary Drug Handbook (VDH) is the reference veterinarians turn to when they want an independent source of information on the drugs that are used in veterinary medicine today.


GONADORELIN

Chemistry - A hormone produced by the hypothalamus, gonadorelin is obtained either from natural sources or is synthetically produced. It is a decapeptide that occurs as white or faintly yellowish-white powder. One gram is soluble in 25 ml of water or in 50 ml of methyl alcohol. 50 mcgof gonadorelin acetate is approximately equivalent to 31 units. The commercially available productin the United States (Cystorelin®¯Ceva) is the diacetate decahydrate salt. It is available as thehydrochloride elsewhere.
Gonadorelin has many synonyms, including: gonadotrophin-releasing hormone (GnRH),
LH/FSH-RH, LH-RH, LH/FSH-RF, LH-RF, gonadoliberin, and luliberin.

Storage, Stability, Compatibility

The manufacturers recommend storing gonadorelin in the refrigerator (2-8°C). There is very little information available on the stability and compatibility of gonadorelin. Because bacterial contamination can inactivate the product, it has been recommended that multi-dose vials be used completely as rapidly as possible.

Pharmacology - GONADORELIN

Gonadorelin stimulates the production and the release of FSH and LH from the anterior pituitary. Secretion of endogenous GnRH from the hypothalamus is thought to be controlled by several factors, including circulating sex hormones.
Gonadorelin causes a surge-like release of FSH and LH after a single injection. In cows and ewes, this can induce ovulation, but not in estrus mares. A constant infusion of gonadorelin will initially stimulate LH and FSH release, but after a period of time, levels will return to baseline.Uses, Indications - Gonadorelin (Cystorelin®¯Ceva; Factrel®¯Fort Dodge) is indicated (approved) for the treatment of ovarian follicular cysts in dairy cattle. Additionally, gonadorelin has been used in cattle to reduce the time interval from calving to first ovulation and to increase the number of ovulations within the first 3 months after calving. This may be particularly important in increasing fertility in cows with retained placenta.
In dogs, gonadorelin has been used experimentally to help diagnose reproductive disorders or to identify intact animals versus castrated ones by maximally stimulating FSH and LH production. It has also been used experimentally in dogs to induce estrus through pulsatile dosing. While apparently effective, specialized administration equipment is required for this method.
Gonadorelin has been used in cats as an alternate therapy to FSH or hCG to induce estrus in catswith prolonged anestrus.
In Europe, a synthetic analogue buserelin, has been used in horses to stimulate cyclic estrus. Itsefficacy is poor when compared to an artificial light program, however.
In human medicine, gonadorelin has been used for the diagnosis of hypothalamic-pituitary dysfunction, cryptorchidism and depression secondary to prolonged severe stress.

Pharmacokinetics - GONADORELIN

After intravenous injection in pigs, gonadorelin is rapidly distributed to extracellular fluid, with a distribution half-life of about 2 minutes. The elimination half-life of gonadorelin is approximately 13 minutes in the pig.
After intravenous injection in humans, gonadorelin reportedly has a plasma half-life of only a fewminutes. Within one hour, approximately half the dose is excreted in the urine as metabolites.
Contraindications/Precautions - None noted.

Adverse Effects, Warnings

No reported adverse reactions were located for this agent.
Synthetically prepared gonadorelin should not cause any hypersensitivity reactions. This may notbe the case with pituitary-obtained LH preparations or hCG.
Overdosage - In doses of up to 120 micrograms/kg, no untoward effects were noted in severalspecies of test animals. Gonadorelin is unlikely to cause significant adverse effects after inadvertentoverdosage.

Drug Interactions

None noted.
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