The GnRH agonist, deslorelin, acts by suppressing the function of the pituitary-gonadal axis when applied in a low, continuous dose. This suppression results in the failure of treated animals, intact or surgically neutered, to synthesise and/or release follicle stimulating hormone (FSH) and luteinising hormone (LH), the hormones responsible for the maintenance of fertility as well as secondary sexual behaviours.

In male dogs or cats, the continuous low dose of deslorelin will reduce the functionality and the size of the male reproductive organs, libido, and spermatogenesis, and lower the plasma testosterone levels, from 4-6 weeks after implantation. A short transient increase in plasma testosterone may be seen immediately after implantation. Measurement of plasma concentrations of testosterone has demonstrated the persistent pharmacological effect of the continuing presence of deslorelin in the circulation for at least six months in dogs and twelve months in cats following administration of the veterinary medicinal product.

In sexually immature female dogs, the continuous low dose of deslorelin maintains dogs in a physiologically immature state and prevents the increase of the plasma oestradiol and progesterone levels. This hormonal downregulation suppresses the development and function of the female reproductive organs and associated sexual heat behavioural signs and changes in vaginal cytology.

It has been shown that plasma deslorelin levels peak 7 to 35 days following administration of an implant containing 5 mg radiolabelled deslorelin. The substance can be directly measured in the plasma up to approximately 2.5 months post implantation. The metabolism of deslorelin is rapid.

In a study investigating pharmacokinetics in cats, it has been shown that plasma deslorelin concentrations peak at 2 hours (Cmax) at around 100 ng/mL followed by a rapid decrease by 92%, 24 hours post implantation. After 48 hours, a slow and continuous decline of plasma deslorelin concentrations was observed. The duration of deslorelin release from Suprelorin implants, calculated as measurable plasma deslorelin concentrations, varied from 51 weeks to at least 71 weeks (the end of the study)