Deslorelin (Suprelorin) is an anti-androgenic hormone used as an off-label treatment for anoestrus and other oestrus disorders in female cats. It has also been used in cats for conditions such as inappropriate elimination.

 

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Deslorelin effects contraception by temporarily suppressing the reproductive endocrine system, preventing production of pituitary (FSH and LH) and gonadal hormones (estradiol and progesterone in females and testosterone in males). Implanted deslorelin appears active in suppressing sexual activity for 8-12 months, although longer periods of anoestrus have been reported^[1]. Unlike other GnRH agonists, which are mainly used to inhibit luteinizing hormone and follicle-stimulating hormone by their ultimate down-regulation of the pituitary gland, Deslorelin is primarily used for the initial flare effect upon the pituitary, and its associated surge of LH secretion^[2].

The observed effects are similar to those following ovariectomy or castration, but are reversed after the hormone content of the implant is depleted. As a hormone agonist, deslorelin first stimulates the reproductive system, which can result in estrus and ovulation in females or temporary enhancement of testosterone and semen production in males. Then down-regulation follows the initial period of stimulation. Deslorelin has been effective in females of a wide range of species, but not in the male ungulates nor some marsupials tested to date^[3].

Efficacy in females can be monitored by estrous behavior. Efficacy in male dogs has correlated well with testosterone suppression, but documentation of absence of sperm may be important in other species. Even after spermatogenesis is interrupted, there may be viable sperm in the ejaculate for weeks or possibly even months, as is the case following vasectomy.

 

Side effects

Trials to date have focused primarily on domestic dogs, although there has been one controlled study in domestic cats and preliminary data from a number of cheetahs and lions^[4]. These investigations have not detected any adverse effects, although weight gain was common, as is often the case following castration or ovariectomy. In all cases where reversibility was tested, reproductive function was fully restored.

In cases of delayed return to normal sexual activity, oestrus can be induced in the Queen with subcutaneous injections (every 3 days) of 200 I.U. Folligon (serum gonadotrophin) until oestrus resumes.

 

Dose

Deslorelin implants are available in two sizes: 4.7 mg and 9.4 mg. The 4.7-mg implant has been found to be effective for 6 to 12 months in domestic dogs, and the 9.4-mg size has been effective for almost 2 years in some female lions. A disadvantage is that the implant is difficult to remove if reversal is desired before the hormone in the implant becomes depleted, since the implant breaks easily. However, careful implant insertion to avoid breakage can facilitate later removal^[5].

 

References

1. ↑ Euclid, JM (2010) Pers comm
2. ↑ Wikipedia.org
3. ↑ Romagnoli S, et al (2009) Clinical use of deslorelin for the control of reproduction in the bitch. Reprod Domest Anim 44(2):36-9
4. ↑ Bertschinger HJ, et al (2001) Control of reproduction and sex related behaviour in exotic wild carnivores with the GnRH analogue deslorelin: preliminary observations. J Reprod Fertil Suppl 57:275-283
5. ↑ Trigg T.E., et al (2006) A review of advances in the use of the GnRH agonist deslorelin in control of reproduction. Theriogenology 66:1507-1512